text:
\section{Introduction}
\label{sec::intro}

The interstellar gases, including those in atomic, molecular, and ionized forms, account for $\sim$99\% of the mass of interstellar medium (ISM), with the rest being interstellar dust. Various molecules exist in the ISM, some of which become the tracers to study the formation of stars \citep{1987ARA&A..25...23S} and planets \citep{1976PThPh..56.1756A, 1980PThPh..64..544M}. Spectral lines of these molecules can be used to derive the gas temperature, velocity, column density, and internal dynamics. Therefore, interstellar molecular spectroscopy have become one of the most commonly used diagnostic tools for ISM.

The first interstellar molecule, CH, was reported to exist through observation of absorption feature in the optical band \citep{1940PASP...52..187M}. After the advent of radio astronomy, many more molecular species were detected thanks to the increasing sensitivity and spatial/spectral resolution of facilities. As of 2021, 241\footnote{At the time of writing, the number of interstellar molecules included in CDMS is 271 (https://cdms.astro.uni-koeln.de/classic/molecules).} \citep{2022ApJS..259...30M} molecular species consisting of 18 elements were reported to exist in ISM or circumstellar envelopes (CSE) (including unconfirmed ones). These molecules are made up of 2$-$70 atoms, and their transition frequencies range from microwave to ultraviolet bands \citep{2022ApJS..259...30M}.

The identification of interstellar molecules, in essence, is to infer the abundances of different molecules and physical parameters of interstellar gas. Technically, this is an optimization problem. It tries to find the best set of parameters with regard to some optimization goal, which is usually the difference between the simulated and observed spectrum. In the case of a positive identification, the individual lines in simulated spectrum is supposed to match those in observation with the right line widths and intensities \citep{2008A&A...482..179B}. The simulated spectrum is calculated using the radiative transfer equation and usually (but not always) under the assumption of local thermodynamic equilibrium (LTE). As key parameters in the radiative transfer equation, molecular spectroscopy data are the foundation of the molecule identification process.

Databases such as the one maintained by Jet Propulsion Laboratory\footnote{\url{https://spec.jpl.nasa.gov/ftp/pub/catalog/catdir.html}} (JPL), the Cologne Database for Molecular Spectroscopy\footnote{\url{https://cdms.astro.uni-koeln.de/classic/entries/}} (CDMS), the HIgh-resolution TRANsmission molecular absorption database\footnote{\url{https://hitran.org}} (HITRAN), and the NIST Atomic Spectra Database \footnote{\url{https://physics.nist.gov/PhysRefData/ASD}} provide spectroscopy data to simulate spectral lines. Among these databases, JPL and CDMS are frequently used by radio astronomers in molecular identification. In this paper we present a meta-analysis of the JPL and CDMS spectroscopic databases.

A meta-analysis of these two databases can tell us which species have the potential to be detected at present and which transition lines are more likely to be resolved under certain astrophysical environments. We can estimate the integration time needed for a certain facility to detect the spectral lines of any molecular species with given astrophysical parameters. In general, a meta-analysis of current molecular databases may provide useful insights for future molecular identification. In Section \ref{sec::Iden_Proc} we present a brief description of radiative transfer, followed up with the meta-analysis of molecular spectroscopy databases in Section \ref{sec::Databases}. We discuss what molecules can be observed and how much time it will cost to observe certain molecular species in Section \ref{sec::Instruction}, followed by a conclusion in Section \ref{sec::conclusion}.

\section{Radiative transfer}
\label{sec::Iden_Proc}
About 90 percent molecules are detected in radio frequency range \citep{2022ApJS..259...30M}. This is mainly because of the composition of molecules and the environment where they reside in: the low temperature of molecular clouds means that the electronic and vibrational emissions of molecules cannot occur (absorption of background sources do sometimes occur); the large moment of inertia of these molecules (except for molecular hydrogen) lead to small rotational constants thus low transition frequencies.

The interactions of radiation field with matter can be expressed by the radiative transfer equation \citep{1979rpa..book.....R} as
\begin{equation}
	\frac{\mathop{}\!\mathrm{d} I_{\nu}}{\mathop{}\!\mathrm{d} s} = -\alpha_{\nu}I_{\nu} + j_{\nu},
\end{equation}
where $\alpha_{\nu}$ and $j_{\nu}$ are the absorption and emission coefficient, respectively, $I_{\nu}$ the specific intensity, $s$ the travel path. This equation can be integrated as
\begin{equation}
	\label{equ::radiative_e}
	I(\nu) = I_{0}(\nu)e^{-\tau_{\nu}} + S_{\nu}(T)(1-e^{-\tau_{\nu}}).
\end{equation}
Here $S_{\nu}$ is referred to as the source function, which in LTE assumption equals the Planck blackbody radiation function $B_{\nu}$ of the same temperature. $ I_{0}(\nu)$ is the background radiation, $T$ the excitation temperature, and $\tau$ the optical depth which is defined as the integration of $\alpha_{\nu}$ along the travel path $s$:
\begin{equation}
	\tau_{\nu} = \int \alpha_{\nu} \mathop{}\!\mathrm{d} s = \frac{c^{2}}{8\pi \nu_{0}^{2}} \frac{g_{u} e^{-E_{l}/kT}}{Q(T)} N_{\mathrm{tot}} A_{ul} [1 - e^{-h\nu_{0}/kT}]\varphi(\nu),
\end{equation}
where $T$ is assumed to be independent of $s$, $c$ the speed of light, $\nu_{0}$ the transition frequency, $g_u$ the statistical weight of the $u$ energy level, $E_l$ the energy of $l$ level, $Q(T)$ the partition function, $N_{\mathrm{tot}}$ the total column density, $A_{ul}$ the Einstein $A$ coefficient, $h$ the Planck constant, $k$ the Boltzmann constant, and $\varphi(\nu)$ the line profile function. The Einstein $A_{ul}$ coefficient describes the probability per unit time of a molecule in an excited energy level $E_{u}$ to return spontaneously to a lower energy level $E_{l}$ \citep{2009tra..book.....W}. $A_{ul}$ is related with the other two Einstein coefficients $B_{ul}$ and $B_{lu}$ via
\begin{equation}
	\label{equ::Aul}
	A_{ul}=\frac{8\pi h\nu_{0}^{3}}{c^{3}}B_{ul},
\end{equation}
\begin{equation}
	\label{equ::Bul}
	g_{l}B_{lu}=g_{u}B_{ul}.
\end{equation}
in which $g_l$ is the statistical weight of the $l$ energy level. Molecular spectroscopy data, including $Q(T)$, $g_{u}$, $E_{l}$, $A_{ul}$, and $\nu_{0}$, are needed when calculating the spectral line intensity, which can be accessed through several databases.

\section{A Meta-analysis of Molecular Spectroscopy Databases}
\label{sec::Databases}

\subsection{The CDMS and JPL spectroscopic databases}
The JPL provides spectroscopy data ``based on the project needs of astronomers" \citep{1998JQSRT..60..883P} and CDMS catalogs ``molecules that are present or are supposed to be present in ISM or CSE or in planetary atmospheres" \citep{muller_cologne_2001}. CDMS/JPL provides spectroscopic data for 1137/401 species, of which 189 are available in both databases. Each line of a data file contains the frequency $\nu$ and its uncertainty, the base 10 logarithm of integrated intensity $I$ at 300\,K, degree of freedom in the rotational partition function, lower state energy $E_{l}$, upper state degeneracy $g_{u}$, and the quantum numbers. These data can be accessed through their websites and downloaded in ASCII format. The Einstein $A$ coefficient can be calculated as \citep{1998JQSRT..60..883P}:
\begin{equation}
	A_{ul}=I(300\,K)\nu^{2}\frac{Q(T)}{g_{u}(e^{-E_{l}/kT}-e^{-E_{u}/kT})}\times2.7964\times10^{-16}
\end{equation}
where $E_{u}$ is the upper state energy. CDMS provides an interface to search for all transitions within a given frequency range, and plot their intensities as a function of frequency under some simple assumptions online \citep{muller_cologne_2005}.

Regarding the 189 species that are included in both the CDMS and JPL databases, their entries can be classified into four cases. Some of them contain completely identical transitions except for the precision of spectroscopy data. The transitions of several species in one database are the subsets of those in another. Some pairs have a part of identical transitions (again, except for the precision) and additional unique ones in each database. The rest pairs are complementary to each other, with no repeating transition.

CDMS also participates in the Virtual Atomic and Molecular Data Centre and provides data in MySQL database format\footnote{\url{http://cdms.ph1.uni-koeln.de/cdms/portal/cdms\_lite.db.gz}} \citep{endres_cologne_2016}. Different from the files directly downloaded from their website, this database file contains the Einstein $A$ coefficients rather than the integrated intensity. Molecular species in JPL are also included in this database file.

\subsection{Transition Frequency Distribution}
\label{sec::Tran_Freq_Distr}

The transition frequencies range from 0.4\,kHz to $\sim$166,000\,GHz in CDMS and 0.4\,kHz to $\sim$857845\,GHz in JPL. In Fig. \ref{fig::trans_distr_AS_All} we show the histogram of transition frequencies of all the species in CDMS and JPL in a log$-$log scale. The number of transitions in each 10,000\,km/s velocity interval rises from $\sim$10 at $\sim$0.01\,MHz to $\sim$100,000 at $\sim$1000\,GHz and then decreases sharply. Quantitatively, about 99\%, 90\%, and 50\% of these frequencies fall in the intervals from 8 to 21,420\,GHz, 70 to 3098\,GHz, and 266 to 985\,GHz, respectively.
\begin{figure}[!htb]
	\centering
	\includegraphics[width=10cm]{pics/ms2022-0236fig1.pdf}
	\caption{Histograms of the transition frequencies of molecules in CDMS and JPL. Each bin represents the velocity width of 10,000\,km/s. Data from CDMS  are in purple and JPL in light green. }
	\label{fig::trans_distr_AS_All}
\end{figure}
Nearly two hundred of transitions have extremely low frequencies ($<10^{-5}$\,GHz), which are all from the rotational transitions of CH$_3$OH, CH$_3^{18}$OH, and H$_2$CO. These three asymmetric top molecules are close to symmetric top structures, so the extremely low energy difference between two energy levels, which is caused by the deviation from the symmetric top case, leads to extremely low transition frequencies. They are calculated in theory but may not be detectable in practice because of the extremely low frequency and intensity.

\subsection{Frequency Uncertainty}

Molecular spectroscopy data are either calculated theoretically or measured in laboratory, and the precision of these data determines the reliability of molecular identification. Files provided by CDMS and JPL include the uncertainty of transition frequencies, which ranges from 0$-$1\,GHz. This frequency error can be translated into a velocity error as
\begin{equation}
	v_{_{\mathrm{err}}} = \frac{\nu_{_{\mathrm{err}}}}{\nu}\cdot c,
\end{equation}
where $\nu$ is the transition frequency and $\nu_{\mathrm{err}}$ represents its uncertainty. Figure \ref{fig::uncer_distr} gives the distribution of frequency uncertainties and velocity errors of all transitions in both CDMS and JPL. Most of these uncertainties are low enough that the majority of velocity errors are under 1\,km/s.

\begin{figure}[!htb]
	\centering
	\includegraphics[width=7cm]{pics/ms2022-0236fig2.pdf}
	\includegraphics[width=7cm]{pics/ms2022-0236fig3.pdf}
	\caption{2D histogram of frequency uncertainties and the corresponding velocity errors in both CDMS and JPL.}
	\label{fig::uncer_distr}
\end{figure}

The internal turbulent motion of gas flows make their radial velocities have a finite velocity width. Assuming a typical velocity width $\Delta v \lesssim$ 10\,km/s (FWHM), if the velocity error of a transition is comparable to or greater than the velocity width, it is difficult to attribute the spectral line to its corresponding molecule. For this reasons, we divided all velocity errors into three levels, $v_{{\mathrm{err}}}<$ 1\,km/s, 1\,km/s $\le v_{{\mathrm{err}}}<$ 10\,km/s, and $v_{{\mathrm{err}}}\ge$ 10\,km/s, as reliable, suspicious, and unreliable, respectively. We assigned the three levels with different colors and drew a velocity error distribution map in Fig. \ref{fig::Uncers_AS_All},
\begin{figure}[!htb]
	\centering
	\includegraphics[width=12cm]{pics/ms2022-0236fig4.jpg}
	\caption{The distribution of velocity errors in a frequency-intensity map. Each pie chart was filled with at most three colors: green, purple, and red, corresponding to fractions of frequencies that are reliable, tentative, and unreliable, respectively. A bigger pie chart means a greater number of transition lines are cataloged in this frequency-intensity range.}
	\label{fig::Uncers_AS_All}
\end{figure}
where we can see that except for those calculated theoretically (uncertainty$=0$\,MHz), spectroscopy data with frequencies lower than 0.1\,GHz are less reliable than those with higher frequencies, and data with higher intensities are also more reliable. All data with relatively low frequencies ($\nu < $0.1 \,GHz) and low intensity ($\lg I_{\nu} < -25$\,$\mathrm{nm^{2}}\cdot \mathrm{MHz}$) have high velocity errors ($v_{{\mathrm{err}}}>$ 10\,km/s), and they are all from the isotopomers of either O$_{2}$ or OH. The relatively large pie charts are in the 100$-$1000\,GHz range, which means more transitions are cataloged in this frequency range. In general, most of these transitions are reliable.

\subsection{Line Confusion}
\label{sec::line_confusion}
If two transition lines have similar intensities, and the separation of line centers is less than either of their line widths, these two lines are considered to be blended, which is known as the line confusion problem. To discuss this issue, we assume that all previously identified molecules are present in an interstellar cloud, and have a constant excitation temperature of 20\,K and an FWHM velocity width of 5\,km/s. The column densities are set to their typical values that obtained from literature\footnote{These values and corresponding references are available on Github: \url{https://github.com/LiuXnhhh/paper_materials}}. Those without definite literature values are all belong to vibrational/electronic excited states or minor isotopomers. For the latter ones we adopt empirical isotope ratios of $\text{H}/\text{D}=1000$ \citep{2013A&A...549L...3P}, $^{12}\text{C}/^{13}\text{C}=59$,  $^{14}\text{N}/^{15}\text{N}=237$, $^{32}\text{S}/^{34}\text{S}=19$ \citep{1998A&A...337..246L}, $^{16}\text{O}/^{18}\text{O}=672$ \citep{1981ApJ...243L..47W}, $^{16}\text{O}/^{17}\text{O}=1935$ \citep{2008A&A...487..237W}, $^{28}\text{Si}/^{29}\text{Si}=13$, $^{28}\text{Si}/^{30}\text{Si}=12$ \citep{1980ApJ...242.1005W}, and $^{35}\text{Cl}/^{37}\text{Cl}=2.1$ \citep{2012ApJ...751L..37D} to derive rough column density values from their main isotopomer instead, while those in vibrational/electronic excited states are not included for the lack of good estimations of their column densities. We must note that the H/D ratio varies dramatically under the influence of difference chemical processes in low temperature, and a reasonable mean value of 1000 is adopted here. We then define the line confusion as the number of spectral lines in each 10\,km/s interval in the simulated spectrum, and arbitrarily call intervals with more than five transitions as ``crowded". Lines with extremely low intensities ($T_{\mathrm{mb}}<0.01$\,K) are not included for line-confusion counting.

Figure \ref{fig::Overlapped_trans} shows the number of crowded intervals in each 1\,GHz bin from 0 to 2000\,GHz,
\begin{figure}[!htb]
	\centering
	\includegraphics[width=12cm]{pics/ms2022-0236fig5.pdf}
	\caption{The distribution of ``crowded" intervals which is defined in Section \ref{sec::line_confusion}. Each bin represents a frequency width of 1\,GHz.}
	\label{fig::Overlapped_trans}
\end{figure}
from which we know that transitions between $\sim$50 and 600\,GHz are more crowded than those in higher or low frequency ranges. Note that all previously detected molecules are included to give an overview of the line confusion, but this may oversimplify the reality. A source is unlikely to have all these molecules, and the excitation conditions of molecules may differ from one to another. Some sources contain multiple velocity components, which may aggravate the problem of line confusion.

\section{Suggestions for Future Observations}
\label{sec::Instruction}

For a given source, we would like to know which transitions can be obtained at certain noise level using a given telescope within a reasonable integration time, and we also want to figure out how much time it would take if we intend to search for certain molecular species, or what physical environment should this molecule reside in if it is detectable.

With regard to these concerns, we investigate the observability of molecules using a few major facilities that would be operating in the future. To calculate the line intensities, we consider three types of ISM environments: i) a cold diffuse source with an angular size ($\theta_{\text{s}}$) of 60\,$''$ and an excitation temperature ($T_{\mathrm{ex}}$) of 10\,K \citep{1997ApJ...486..862P}; ii) a hot dense core with an angular size of 3\,$''$ and an excitation temperature of 200\,K \citep{2013A&A...559A..47B}; iii) an intermediate case with an angular size of 40\,$''$ and an excitation temperature of 30\,K. These three cases are summarized in Table \ref{tab::common_environment}.
\begin{table}[!htb]\small
	\begin{center}
		\caption[]{Three sets of assumed physical parameters for simulating molecular spectra.}\label{tab::common_environment}
		\begin{tabular}[5pt]{ccc}
			\hline\noalign{\smallskip}
			&  $T_{\mathrm{ex}}$ (K) & $\theta_{\text{s}}$ ($''$)  \\
			\hline\noalign{\smallskip}
			Case 1  & 10 & 60 \\
			Case 2 & 200 & 3 \\
			Case 3 & 30 & 40 \\
			\noalign{\smallskip}\hline
		\end{tabular}
	\end{center}
\end{table}
Column densities are set to their typical measured values, as mentioned in Section \ref{sec::line_confusion}. A typical line width of 5\,km/s is assumed for all lines. The beam filling factor for a source $s$ is defined as
\begin{equation}
	\eta_{\text{s}} = \frac{\theta_{\text{s}}^{2}}{\theta_{\text{s}}^{2}+\theta_{\text{t}}^{2}},
\end{equation}
where $\theta_{\text{t}}$ is the half-power beamwidth of a telescope. This factor becomes important when the source is not extended. The cosmic microwave background (CMB) radiation ($T_{_{\mathrm{CMB}}}=2.725$\,K) is also considered. Lines with the peak intensities higher than three times sensitivity ($\sigma$) are taken as detectable, and molecular species with more than three detectable transitions are regarded as unambiguous identifications \citep{2005ApJ...619..914S}. Molecular spectroscopy data used in this section are mainly taken from CDMS and is supplemented by those in JPL. Note that the column densities of nearly one third of molecules are derived from empirical isotope ratios. These molecules are either minor isotopomers or in a vibrational/electronic excited state thus may be less abundant than assumed, causing the overestimation of their line intensities. Thus the detectabilities stated here can only be viewed as an optimistic estimation, and is valid only for molecules under LTE conditions. To ensure the reliability of the predictions, we have compared the synthesized spectra with the line survey reported by \citet{2013A&A...559A..47B} using the same physical parameters. Results show that our simulated lines are almost identical to their synthetic spectra. We will benchmark the performance of current spectral line modeling programs and discuss this in future.

\subsection{The Terahertz module of CSST}

The high-sensitivity terahertz detection module (HSTDM) \citep{8563600} onboard Chinese Space Station Telescope (CSST) covers a frequency range of 410$-$510\,GHz. CSST has a diameter of 2\,m, which means at the working band of HSTDM the beamwidth is $\sim$70\,$''$. With a frequency resolution of 0.1 MHz, the receiver promises to be able to reach a $3\sigma$ noise level of 0.15\,K with 200\,s of integration.

\subsubsection{Molecules that are observable in one hour}
Among all previously identified molecules and their isotopomers, 25/21/58 of them can be detected by CSST/HSTDM within one hour in case 1/2/3, respectively (see Tables \ref{tab::all_detectable_CSST_1}, \ref{tab::all_detectable_CSST_2}, and \ref{tab::all_detectable_CSST_3}). We take two molecules of special significance or with relatively more detectable transitions as examples and discuss their observability in detail.

\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules with one hour of integration by CSST/HSTDM in case 1.}\label{tab::all_detectable_CSST_1}
		\begin{tabular}[5pt]{lllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms  & 4 Atoms & 5 Atoms & 6 Atoms& 8 Atoms & 9 Atoms  \\
			\hline\noalign{\smallskip}
			$\mathrm{CN}$	 & $\mathrm{C_{2}H}$	 & $\mathrm{DNCO}$	 & $\mathrm{CH_{2}NH}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{CH_{3}CH_{2}CN}$	\\
			$\mathrm{NO}$	 & $\mathrm{DCO^{+}}$	 & $\mathrm{H_{2}CO}$	 & $\mathrm{HCOCN}$	 & $\mathrm{CH_{3}OH}$	 & 	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	\\
			& $\mathrm{H_{2}Cl^{+}}$	 & $\mathrm{HONO}$	 & $\mathrm{HNCNH}$	 & $\mathrm{H_{2}CCNH}$	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	\\
			& $\mathrm{NH_{2}}$	 & $\mathrm{NH_{2}D}$	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	\\
			& $\mathrm{SO_{2}}$	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}OCH_{3}}$	\\
			& $\mathrm{Si_{2}C}$	 & 	 & 	 & 	 & 	 & 	\\
			& $\mathrm{TiO_{2}}$	 & 	 & 	 & 	 & 	 & 	\\
			\noalign{\smallskip}\hline
		\end{tabular}
	\end{center}
\end{table}
\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules with one hour of integration by CSST/HSTDM in case 2.}
		\label{tab::all_detectable_CSST_2}
		\begin{tabular}[5pt]{lllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms  & 5 Atoms & 6 Atoms  & 8 Atoms & 9 Atoms & $>$  9 Atoms \\
			\hline\noalign{\smallskip}
			$\mathrm{AlO}$	 & $\mathrm{AlOH}$	 & $\mathrm{HC_{3}N}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{CH_{3}CH_{2}CN}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			$\mathrm{CN}$	 & $\mathrm{DCO^{+}}$	 & 	 & $\mathrm{CH_{3}OH}$	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			$\mathrm{PO}$	 & $\mathrm{SO_{2}}$	 & 	 & $\mathrm{H_{2}CCNH}$	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 &  \\
			$\mathrm{TiO}$	 & $\mathrm{TiO_{2}}$	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	 &  \\
			&	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
		\vspace*{-1.5ex}
		\tablecomments{0.86\textwidth}{The descriptor ``$i$-" ($iso$) of $\mathrm{C_{3}H_{7}CN}$ means the four C atoms form a branched skeleton.}
	\end{center}
\end{table}
\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules with one hour of integration by CSST/HSTDM in case 3.}\label{tab::all_detectable_CSST_3}
		\begin{tabular}[5pt]{lllllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms & 4 Atoms & 5 Atoms & 6 Atoms & 7 Atoms& 8 Atoms  & 9 Atoms & $>$  9 Atoms \\
			\hline\noalign{\smallskip}
			$\mathrm{AlF}$	 & $\mathrm{AlOH}$	 & $\mathrm{DNCO}$	 & $\mathrm{CH_{3}Cl}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $c$-$\mathrm{C_{2}H_{4}O}$	 & $\mathrm{CH_{2}OHCHO}$	 & $\mathrm{^{13}\!CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{CH_{3}CH_{2}OCHO}$ \\
			$\mathrm{AlO}$	 & $\mathrm{C_{2}H}$	 & $\mathrm{H_{2}^{13}\!CO}$ $\!^{*}$	 & $\mathrm{CH_{3}^{37}\!Cl}$	 & $\mathrm{CH_{3}OH}$	 & $s$-$\mathrm{H_{2}CCHOH}$	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}^{13}\!CN}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			$\mathrm{^{13}\!CN}$	 & $\mathrm{DCO^{+}}$	 & $\mathrm{H_{2}CO}$	 & $\mathrm{H_{2}CNH}$	 & $\mathrm{H_{2}CCNH}$	 & 	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	& $aGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			$\mathrm{CN}$	 & $\mathrm{H_{2}Cl^{+}}$	 & $\mathrm{HNCO}$	 & $\mathrm{HCOCN}$	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	& $gGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			$\mathrm{FeO}$	 & $\mathrm{HNO}$	 & $\mathrm{HONO}$	 & $\mathrm{HNCNH}$	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			$\mathrm{NO}$	 & $\mathrm{NH_{2}}$	 & $\mathrm{NH_{2}D}$	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{2}DCH_{2}CN}$ $\!^{*}$	 & $n$-$\mathrm{C_{3}H_{7}CN}$ \\
			$\mathrm{NS}$	 & $\mathrm{SO_{2}}$	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}^{13}\!CN}$	 &  \\
			$\mathrm{PO}$	 & $\mathrm{Si_{2}C}$	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 &  \\
			$\mathrm{SO}$	 & $\mathrm{TiO_{2}}$	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}CN}$	 &  \\
			$\mathrm{SiC}$	 & 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}OH}$	 &  \\
			$\mathrm{SiN}$	 & 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CHDCN}$ $\!^{*}$	 &  \\
			$\mathrm{TiO}$	 & 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}OCH_{3}}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
		\vspace*{-1.5ex}
		\tablecomments{0.86\textwidth}{$^{*}$Molecules with column densities derived from their main isotopomer. The descriptor ``$c$-" in $c$-$\mathrm{C_{2}H_{4}O}$ represents the O atom and two C atoms that are arranged in a $cyclic$ form. The ``$s$-" in $s$-$\mathrm{H_{2}CCHOH}$ means the ``$syn$-" form of the the molecule, with the H atom in hydroxyl and CH$_2$ ridical on the same side of the C$-$O bond. The ``$aGg'$-" and ``$gGg'$-" represent two rotational isomers of $\mathrm{(CH_{2}OH)_{2}}$: $G$ ($gauche$) means two hydroxymethyls are $\pm$60$^{\circ}$ apart, and $a$ ($anti$), $g$, $g'$ mean the hydroxyl and hydroxymethyl are 180$^{\circ}$ , 60$^{\circ}$, and -60$^{\circ}$ apart, repsectively. The ``$n$-" ($normal$) means the four C atoms in $\mathrm{C_{3}H_{7}CN}$ are arranged in a straight chain.}
	\end{center}
\end{table}

\paragraph{CH$_3$OH and $^{13}$CH$_3$OH} In case 1/2/3, 48/60/135 transition lines of CH$_3$OH and 98/322/265 lines of $^{13}$CH$_3$OH can be detected within one hour. As one of the most prominent molecules expected to be detected by CSST/HSTDM, several transitions of $^{13}$CH$_3$OH in 234$-$238\,GHz \citep{1985ApJS...58..341S} and 488 to 571\,GHz \citep{2007A&A...476..807P} have already been detected in different lines of sight. Interstellar CH$_3$OH, the main isotopomer of $^{13}$CH$_3$OH, can be used to trace the interface between outflows and ambient gas \citep{1990ApJ...364..555P} and compact H \textsc{ii} regions \citep{1987Natur.326...49B}, and is thought to be related to the formation of complex organic molecules \citep{2009A&A...504..891O}. Since both $^{13}$CH$_3$OH and CH$_3$OH can be detected by CSST/HSTDM in all three cases, one can use them to derive the $^{13}$C/$^{12}$C ratio.

We have considered three assumed cases to give an overview of which molecules can be detected, but they may not be the environments where CH$_3$OH and $^{13}$CH$_3$OH reside in. More realistically, we revisit the spectral lines of $^{13}$CH$_3$OH and CH$_3$OH which reside in Orion-KL with an angular size of 12\,$''$ \citep{Schilke_2001} and different excitation temperatures. Results show that they both can be detected when the excitation temperature is higher than $\sim$12\,K.

\paragraph{CN} The high frequency resolution of CSST/HSTDM enables the detection of CN and its hyper-fine components at $\sim$453\,GHz. The Zeeman effect of CN can be used as a direct measurement of strengths of magnetic fields \citep{1996ApJ...456..217C} and has already been detected toward a few dense clouds through its $N=1\to 0$ transition at $\sim$113\,GHz \citep{1999ApJ...514L.121C}. The CN $N=4\to3$ transition (452$-$454\,GHz) has 19 hyper-fine components, of which six have relatively strong intensities. We adopt an average angular size of 58\,$''$ \citep{2002ApJ...578..211S} for several galactic molecular clouds, and find that these six lines are detectable from $T_{\mathrm{ex}}\simeq$ 8\,K all along to $\sim$300\,K. But according to the project plan of CSST/HSTDM, polarization capability for measuring magnetic field with the Zeeman effect is not implemented.

\subsubsection{Prebiotic molecules}

Prebiotic molecules are those ``that are thought to be involved in the processes leading to the origin of life'' \citep{2009ARA&A..47..427H}. Amino acids, the basic building blocks of living creatures, are one of the prebiotic molecules most searched for by astronomers. \cite{1970Natur.228..923K} discovered five abundant amino acids in meteorites, and now more than 80 species of amino acids were detected in meteorites (\citealt{1997Sci...275..951C, 2017NatSR...7..636K}, etc.). While no spectral line of interstellar amino acids has been unambiguously confirmed, their possible precursors such as formic acid (HCOOH) \citep{1971ApJ...163L..41Z}, amino acetonitrile (NH$_2$CH$_2$CN) \citep{2008A&A...482..179B}, and isocyanic acid (HNCO) \citep{1972ApJ...177..619S} have been detected. We carried out several simulations on observing prebiotic molecules to investigate how long it would take if we would like to detect them in different astrophysical environments.
\paragraph{Glycine} As the simplest amino acid, glycine (H$_{\mathrm{2}}$NCH$_{\mathrm{2}}$COOH) can form on the analogous of interstellar grains \citep{2002Natur.416..401B}. Several attempts \citep{2007MNRAS.376.1201C, 2007MNRAS.374..579J} had been made to search for its lowest energy conformer I and higher energy conformer II, but failed. In the consideration of an unambiguous identification, we choose three brightest lines of glycine conformer I (hereafter glycine, for convenience) to investigate their detectability under a wider range of $(T_\text{ex}, N_\text{tot})$ combinations. The difference between three cases in Table \ref{tab::common_environment} thus only lies in the source sizes, which behave as the dilution factor of line intensities. To avoid redundance, we only discuss the detectability of glycine under case 3 (hereafter for all prebiotic molecule discussions). For each line we draw a detectability plot in Fig. \ref{fig::glycine_obs_CSST}, where the integration time requirement for detecting glycine under a certain combination of ($T_{\mathrm{ex}}$, $N_{\mathrm{tot}}$) can be figured out.
\begin{figure}[!htb]
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig6.pdf}
	\caption{Integration time requirement for CSST/HSTDM to observe three different transitions of glycine. Each pixel in the figure represents a $(T_\text{ex}, N_\text{tot})$ combination, while the color scale indicates the integration time needed for a $3\sigma$ detection, with more than 100 hours set to white.  Red, magenta, and blue contours mark out $(T_\text{ex}, N_\text{tot})$ combinations required for each transition to be detected with an integration time of 10 minutes, 1 hour, and 10 hours, respectively.}
	\label{fig::glycine_obs_CSST}
\end{figure}
\citet{2007MNRAS.374..579J} assumed an excitation temperature of $75$\,K and derived an upper limit of $1.4 \times 10^{15}$\,cm$^{-2}$ for the column density for extend ($\eta = 1$) glycine in an eight-hour observation. As a comparison, assuming the same excitation temperature, CSST/HSTDM could possibly detect glycine with a column density of ${\sim}1 \times 10^{15}$\,cm$^{-2}$ in 10 hr even though a smaller beam filling factor ($\eta \simeq0.23$) is adopted. However, we must note that the actual column density of interstellar glycine (if it exists) could be much lower than the value we assumed here.

\paragraph{Alanine} Same as glycine, alanine (CH$_3$CHNH$_2$COOH) is also able to form on the analogous of interstellar grains and has two conformers. More importantly, it is one of the only two amino acids (besides glycine) included in CDMS. The detectability of alanine is shown in Fig. \ref{fig::alanine_obs_CSST}.
\begin{figure}[!htb]
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig7.pdf}
	\caption{Integration time requirement for CSST/HSTDM to observe three transitions of alanine.}
	\label{fig::alanine_obs_CSST}
\end{figure}
Compared with those of glycine, the spectral lines of alanine is fainter thus more difficult to be detected with CSST/HSTDM.

\paragraph{c-HCOOH}\footnote{The descriptor ``$c$-" represent the two H atoms are on the same side of C-O single bond.} According to \citet{2016A&A...596L...1C}, c-HCOOH is thought to be formed via  fluorescent decay from excited t-HCOOH in ultraviolet irradiated gas, making c-HCOOH not only a related species of amino acids but a tracer of photodissociation regions. Limited by its low column density, this molecule was only detected using the line stacking analysis and $T_{\text{ex}}\simeq21$\,K and $N_{\text{tot}} \simeq 4 \times 10^{12}$\,cm$^{-2}$ was derived \citep{2016A&A...596L...1C}. We can tell from Fig. \ref{fig::cHCOOH_obs_CSST} that CSST/HSTDM could detect c-HCOOH with the same temperature and column density in about 20 hr using regular methods.
\begin{figure}
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig8.pdf}
	\caption{Integration time requirement for CSST/HSTDM to observe three transitions of c-HCOOH.}
	\label{fig::cHCOOH_obs_CSST}
\end{figure}

As to the line confusion problem, if all previously identified molecules are present as we assumed, lines of these prebiotic molecules may be blended by those of others. More explicitly, among above-mentioned strong lines, the 413.246296\,GHz line of glycine is slightly blended by previously identified molecules; all three c-HCOOH lines are blended, but its several weaker lines around 455 and 509\,GHz are free from confusion.

\subsection{SKA-mid}

The mid-frequency range (0.58$-$25\,GHz) of the initial phase of Square Kilometer Array (hereafter SKA1-mid) will consist of 133 15\,m SKA1 dishes and 64 13.5\,m MeerKAT telescopes\footnote{\url{https://www.skatelescope.org/wp-content/uploads/2021/02/22380\_Construction-Proposal\_DIGITAL\_v3.pdf}}. By means of interferometry, SKA1-mid can reach a high angular resolution ($\eta\simeq$1). Taking advantages of the frequency resolution (13.44\,kHz) and sensitivity (a system temperature of $\sim$33\,K at 10\,GHz), SKA1-mid can be used to search for amino acids and other prebiotic molecules \citep{2004NewAR..48..979C}.

\subsubsection{Molecules that are observable in one hour}

Because of the higher mass and larger sizes, more complex molecules have larger moment of inertia. The same quantized angular momentum corresponds to lower energy levels. Compared with CSST/HSTDM, SKA1-mid covers a lower frequency range, making it more capable of detecting complex molecules. As shown in Table \ref{tab::all_detectable_SKA_1}, \ref{tab::all_detectable_SKA_2}, and \ref{tab::all_detectable_SKA_3}, more complex molecules, especially carbon chain molecules (C$_{\mathrm{n}}$H, HC$_{\mathrm{2n+1}}$N, etc.), are detectable in one hour under all three cases.

\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules with one hour of integration by SKA1-mid in case 1.}\label{tab::all_detectable_SKA_1}
		\begin{tabular}[5pt]{lllllllll}
			\hline\noalign{\smallskip}
			2 Atoms & 3 Atoms & 4 Atoms & 5 Atoms & 6 Atoms & 7 Atoms & 8 Atoms & 9 Atoms & $>$  9 Atoms \\
			$\mathrm{OH}$	 & $\mathrm{MgNC}$	 & $\mathrm{C_{3}S}$	 & $\mathrm{C_{4}H}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{HC_{5}N}$	 & $\mathrm{^{13}\!CH_{2}OHCHO}$ $\!^{*}$	 & $\mathrm{^{13}\!CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{C_{2}H_{5}NCO}$ \\
			& $\mathrm{NaCN}$	 & $\mathrm{DNCO}$	 & $\mathrm{HCOCN}$	 & $\mathrm{C_{5}H}$	 & $\mathrm{MgC_{5}N}$	 & $\mathrm{CH_{2}OH^{13}\!CHO}$ $\!^{*}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}^{13}\!CN}$	 & $\mathrm{CH_{3}CH_{2}OCHO}$ \\
			& $\mathrm{SO_{2}}$	 & $\mathrm{HONO}$	 & $\mathrm{MgC_{3}N}$	 & $\mathrm{C_{5}N^{-}}$	 & $c$-$\mathrm{C_{2}H_{4}O}$	 & $\mathrm{CH_{2}OHCHO}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			& $\mathrm{Si_{2}C}$	 & $\mathrm{^{15}\!NH_{3}}$	 & $\mathrm{SiC_{4}}$	 & $\mathrm{CH_{3}OH}$	 & 	 & $\mathrm{H_{2}C_{6}}$	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	& $aGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& $\mathrm{TiO_{2}}$	 & $\mathrm{NH_{3}}$	 & 	 & $\mathrm{H_{2}CCNH}$	 & 	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	& $gGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{C_{8}H}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	& $\mathrm{CH_{2}D^{oop}CH_{2}CN}$ $\!^{*}$	 & $n$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}^{13}\!CN}$	 & $s$-$\mathrm{C_{2}H_{5}CHO}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}OH}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}SH}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CHDCN}$ $\!^{*}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}OCH_{3}}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{HC_{7}N}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
		\vspace*{-1.5ex}
		\tablecomments{0.86\textwidth}{The superscript ``$^{\text{oop}}$" in $\mathrm{CH_{2}D^{oop}CH_{2}CN}$ means the D atom are out of the C$_S$ plane. The prefix ``$s$-" of $\mathrm{C_{2}H_{5}CHO}$ represents the formyl and methyl are 0$^{\circ}$ apart from each other.}
	\end{center}
\end{table}
\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules with one hour of integration by SKA1-mid in case 2.}\label{tab::all_detectable_SKA_2}
		\begin{tabular}[5pt]{llllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms & 4 Atoms & 6 Atoms & 7 Atoms  & 8 Atoms & 9 Atoms & $>$  9 Atoms \\
			\hline\noalign{\smallskip}
			$\mathrm{OH}$	 & $\mathrm{SO_{2}}$	 & $\mathrm{^{15}\!NH_{3}}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{HC_{5}N}$	 & $\mathrm{CH_{2}OHCHO}$	 & $\mathrm{^{13}\!CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{CH_{3}CH_{2}OCHO}$ \\
			& $\mathrm{TiO_{2}}$	 & $\mathrm{NH_{2}D}$	 & $\mathrm{CH_{3}OH}$	 & 	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}^{13}\!CN}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			& 	 & $\mathrm{NH_{3}}$	 & $\mathrm{H_{2}CCNH}$	 & 	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	& $aGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	& $gGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	& $\mathrm{CH_{2}D^{oop}CH_{2}CN}$ $\!^{*}$	 & $n$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}^{13}\!CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CHDCN}$ $\!^{*}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
	\end{center}
\end{table}
\begin{table}\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules with one hour of integration by SKA1-mid in Case 3.}\label{tab::all_detectable_SKA_3}
		\begin{tabular}[5pt]{lllllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms & 4 Atoms & 5 Atoms & 6 Atoms & 7 Atoms  & 8 Atoms & 9 Atoms & $>$  9 Atoms \\
			\hline\noalign{\smallskip}
			$\mathrm{OH}$	 & $\mathrm{SO_{2}}$	 & $\mathrm{HONO}$	 & $\mathrm{C_{4}H}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{HC_{5}N}$	 & $\mathrm{CH_{2}OHCHO}$	 & $\mathrm{^{13}\!CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{CH_{3}CH_{2}OCHO}$ \\
			& $\mathrm{Si_{2}C}$	 & $\mathrm{^{15}\!NH_{3}}$	 & $\mathrm{HCOCN}$	 & $\mathrm{CH_{3}OH}$	 & $c$-$\mathrm{C_{2}H_{4}O}$	 & $\mathrm{H_{2}C_{6}}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}^{13}\!CN}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			& $\mathrm{TiO_{2}}$	 & $\mathrm{NH_{2}D}$	 & $\mathrm{SiC_{4}}$	 & $\mathrm{H_{2}CCNH}$	 & 	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	& $aGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & $\mathrm{NH_{3}}$	 & 	 & 	 & 	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	& $gGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	& $\mathrm{CH_{2}D^{oop}CH_{2}CN}$ $\!^{*}$	 & $n$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}^{13}\!CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}CN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}SH}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CHDCN}$ $\!^{*}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}OCH_{3}}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{HC_{7}N}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
	\end{center}
\end{table}

\paragraph{HC$_{\mathrm{2n+1}}$N} Such carbon chain molecules are generally abundant in early stage dense molecular cores before carbon atoms become locked in CO \citep{2013ChRv..113.8981S}. Therefore, they can be used as tracers of dark clouds and starless cores. The case 1 have a similar physical environment with TMC-1, where HC$_5$N, HC$_7$N, HC$_9$N, and HC$_{11}$N have already been detected \citep{1976ApJ...205L.173A, 1978ApJ...223L.105B, 1978ApJ...219L.133K, 2021NatAs...5..188L}. Towards the same source, SKA1-mid can detect HC$_5$N within 5 seconds, HC$_7$N in 10 minutes, and HC$_9$N in 4 hr. \citet{2021NatAs...5..188L} derived an excitation temperature of 6.6\,K and a velocity width of 0.117\,km/s for HC$_{11}$N using line stacking techniques. We use the same parameters as them and find that three brightest HC$_{11}$N lines can be individually detected by SKA1-mid without stacking in 10 minutes.

\subsubsection{Prebiotic molecules}
\label{sec::SKA_prebiotic}

\paragraph{Glycine and alanine} In Fig. \ref{fig::glycine_alanine_obs_SKA} we present the detectability of glycine and alanine using SKA1-mid. If the typical temperature of a cold dense molecular cloud is set to $\sim$35\,K \citep{1979MNRAS.186P...5B}, glycine molecules with column densities of ${\sim}1 \times 10^{15}$\,cm$^{-2}$ can be detected in 10 hr. The same holds for alanine.
\begin{figure}[!htb]
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig9.pdf}
	\vspace{-4mm}

	\includegraphics[width=14cm]{pics/ms2022-0236fig10.pdf}
	\caption{Integration time requirement for SKA1-mid to observe three transitions of glycine (\emph{top}) and alanine (\emph{bottom}).}
	\label{fig::glycine_alanine_obs_SKA}
\end{figure}

\paragraph{Ethanolamine} As the simplest phospholipid head group, ethanolamine (NH$_2$CH$_2$CH$_2$OH) has been identified by  \citet{2021PNAS..11801314R} with $T_{\text{ex}}\simeq 10$\,K and $N_{\mathrm{tot}} \simeq 1.5 \times 10^{13}$\,cm$^{-2}$. For the same excitation temperature and column density SKA1-mid can detect it within 30 hr, as seen in Fig. \ref{fig::NH2CH2CH2OH_SKA}.
\begin{figure}[!htb]
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig11.pdf}
	\caption{Integration time requirement for SKA1-mid to observe three transitions of NH$_2$CH$_2$CH$_2$OH.}
	\label{fig::NH2CH2CH2OH_SKA}
\end{figure}

\paragraph{Amino acetonitrile} As a possible direct precursor of glycine, amino acetonitrile (H$_2$NCH$_2$CN) is thought to be abundant in ISM \citep{2005GeCoA..69..599P}, and has already been identified by \citet{2008A&A...482..179B} with $T_{\text{ex}}\simeq 100$\,K and $N_{\mathrm{tot}} \simeq 2.8 \times 10^{16}$\,cm$^{-2}$. We present the detectability of H$_2$NCH$_2$CN in Fig. \ref{fig::H2NCH2CN_SKA}. It shows that SKA1-mid can detect H$_2$NCH$_2$CN in 10 hr even if the column density is two orders of magnitude lower.
\begin{figure}[!htb]
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig12.pdf}
	\caption{Integration time requirement for SKA1-mid to observe three transitions of H$_2$NCH$_2$CN.}
	\label{fig::H2NCH2CN_SKA}
\end{figure}

The working band of SKA1-mid is less crowded than that of CSST/HSTDM, making these prebiotic molecules more possible to be unambiguously identified. More than ten strong lines of glycine and alanine are unblended or only weakly blended by those of previously identified molecules. Although the three strongest amino acetonitrile lines present in Fig. \ref{fig::H2NCH2CN_SKA} are all weakly blended, several weaker lines are free from line confusion.

\subsection{FAST}

Compared with two telescopes mentioned above, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at present covers a narrower frequency range from 1.05 to 1.45\,GHz, and has a frequency resolution of $\sim$0.48\,kHz. The beamwidth decreases from $\sim$251\,$''$ at 1\,GHz to 140\,$''$ at 1.8\,GHz with a diameter of 300\,m. For simplicity we adopt a constant system temperature of 24\,K \citep{2020RAA....20...64J}, yielding a 3$\sigma$ noise level of $\sim$2.32\,K at 1.4\,GHz in 1 second. Limited by the frequency coverage, only $\mathrm{^{13}\!CH_{3}OH}$ in cases 3 can be detected by FAST within one hour.

If the frequency coverage can slightly extend to a higher range, the OH molecule can be detected by FAST via its four ground state lines: $\mathrm{^{2}\Pi_{3/2}}$ (J=3/2) at 1665.4018 (F=1-1), 1667.3590 (F=2-2), 1612.2310 (F=1-2), and 1720.5300\,MHz (F=2-1). The maser emission of the $\sim$1665 and 1667\,MHz lines are associated with star-forming and their ambient ultracompact H \textsc{ii} regions \citep{1998MNRAS.297..215C}; the 1612\,MHz maser line is used to trace the shell structure of evolved stars \citep{1972A&A....16..204H}; the 1720\,MHz maser line is known to be a probe of shocks \citep{1999ApJ...511..235L}. All these four OH maser lines have been detect by Arecibo telescope \citep{1997ApJS..109..489L, 2018PhRvL.120f1302K}. Using the same facility, \citet{2008ApJ...680..457T} conducted $\sim$500 hr of OH Zeeman observations to derive the magnetic field of nine dark cloud cores, and \citet{2013ApJ...763....8M} measured the Zeeman effect of two main maser lines (1665 and 1669\,MHz). As the largest single-aperture telescope, FAST should be able to detect these four lines as well as their possible maser emission and Zeeman effect.

However, our estimation shows that no prebiotic molecules can be unambiguously detected by FAST within 100 hr  with its current receiver system.

\subsection{Detection by absorption in the presence of a background continuum source}
Since many complex organic molecules were detected in massive star-forming regions \citep{2013A&A...559A..47B}, we calculate the spectral lines of prebiotic molecules that are present in front of a bright source, as sketched in Fig. \ref{fig::bg_fg_sketch}. The background source is taken to be a blackbody.

\begin{figure}[!htb]
	\centering
	\scalebox{0.6}{
	\begin{tikzpicture}
		\draw[line width = 3pt](0, 6)--(0,0);
		\node[rectangle,fill=white,inner sep=0pt] (CMB) at (-0.7,3) {$\text{CMB}$};
		\draw[line width = 1pt, color=cyan](12,3) -- ++(170:9);
		\draw[line width = 1pt, color=cyan](12,3) -- ++(190:9);
		\fill[cyan, opacity = 0.3](3.8,3)ellipse[x radius=0.6,y radius=1.42];
		\draw[cyan, line width=1pt] ([shift=(170:4)]12,3) arc (170:190:4);
		\node[rectangle,fill=white,inner sep=0pt] (fg) at (7.5,3) {\textcolor{cyan}{$\theta_{\text{fg}}$}};
		\node[star, fill=red, inner sep=7.42pt](star) at (1.9,2.948) {\textcolor{red}{a}};
		\draw[line width = 1pt, color=red](12,3) -- ++(176:10.5);
		\draw[line width = 1pt, color=red](12,3) -- ++(184:10.5);
		\draw[red, line width=1pt] ([shift=(176:2.6)]12,3) arc (176:184:2.6);
		\node[rectangle,fill=white,inner sep=0pt] (fg) at (8.8,3) {\textcolor{red}{$\theta_{\text{bg}}$}};
		\draw[line width = 1pt](12,3) -- ++(195:11);
		\draw[line width = 1pt](12,3) -- ++(165:11);
		\draw[line width=1pt] ([shift=(165:6)]12,3) arc (165:195:6);
		\node[rectangle,fill=white,inner sep=0pt] (fg) at (5.7,3) {$\theta_{\text{t}}$};
	\end{tikzpicture}}
	\caption{A sketch of molecular gas (cyan) in front of a background continuum source (red) and CMB (black). Here $\theta_{\text{bg}}$, $\theta_{\text{fg}}$, $\theta_{\text{t}}$ represent the angular sizes of background, foreground, and telescope, respectively.}
	\label{fig::bg_fg_sketch}
\end{figure}
Equation \ref{equ::radiative_e}, taking CMB and filling factors into consideration, can be rewritten as:
\begin{equation}
	I(\nu) = [\eta_{\text{fg}}S_{\nu}(T_{\text{fg}})-\eta_{\text{fg}}S_{\nu}(T_{_{\text{CMB}}}) - \eta_{\text{bg}}B_{\nu}(T_{{\text{bg}}})](1-e^{-\tau_{\nu}}),
\end{equation}
where $T_{\mathrm{bg}}$ represents the temperature of background source, $\eta_{\text{fg}}$ and $\eta_{\text{bg}}$ the filling factors of foreground molecules and the background source, respectively. The $I(\nu)$ here represents the intensity difference between transition lines and the background continuum (i.e. the spectral baseline has been subtracted), one thus may obtain a negative spectral line intensity, i. e. absorption line, if the $\eta_{\text{bg}}B_{\nu}(T_{{\text{bg}}})$ term exceeds the first two terms. Absorption lines with the minimum intensities 3$\sigma$ lower than the local continuum are taken as detectable. Parameters in cases 1, 2, and 3 remain unaltered except for a background source with a temperature of 200\,K and an angular size ($\theta_{\text{bg}}$) of 0.$''$5, which resembles a hot core in Sagittarius B2 molecular cloud \citep{2017A&A...604A..60B}.

The extremely small $\eta_{\text{bg}}$ for CSST/HSTDM ($\sim$10$^{-5}$) and FAST ($\sim$10$^{-6}$) make the spectra almost identical to those with no background source, namely, no absorption feature can be observed with the parameter set assumed here. For SKA1-mid, we continue to assume $\eta_{\text{bg}}=1$ thus a brightness temperature of 200\,K for the background continuum. That is to say, in case 2 of Table \ref{tab::common_environment}, when the excitation temperature of the foreground source is around 200\,K, the small difference between the background and foreground temperature will lead to a low line intensity thus requires a large amount of integration time. For this reason, only $\mathrm{NH_{3}}$, $\mathrm{CH_{3}CH_{2}CN}$, $\mathrm{^{13}\!CH_{3}OH}$, i-$\mathrm{C_{3}H_{7}CN}$, $\mathrm{^{15}\!NH_{3}}$, $\mathrm{OH}$, $\mathrm{C_{2}H_{5}^{13}\!CN}$, and $\mathrm{CH_{3}^{13}\!CH_{2}CN}$ can be detected by SKA1-mid within one hour in this case. Detectable molecules under cases 1 and 3 within one hour using SKA1-mid are listed in Tables \ref{tab::all_detectable_SKA_1_absor} and \ref{tab::all_detectable_SKA_3_absor}, respectively. Many more molecules can be detected in case 1 and 3 when introducing the background source.

\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules in front of a bright source with one hour of integration by SKA1-mid in case 1.}
		\label{tab::all_detectable_SKA_1_absor}
		\begin{tabular}[5pt]{lllllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms & 4 Atoms & 5 Atoms & 6 Atoms & 7 Atoms  & 8 Atoms & 9 Atoms & $>$  9 Atoms \\
			\hline\noalign{\smallskip}
			$\mathrm{CH}$	 & $\mathrm{C_{2}S}$	 & $\mathrm{C_{3}N}$	 & $\mathrm{C_{4}H}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{C_{6}H}$	 & $\mathrm{^{13}\!CH_{2}OHCHO}$ $\!^{*}$	 & $\mathrm{^{13}\!CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{C_{2}H_{5}NCO}$ \\
			$\mathrm{KCl}$	 & $\mathrm{CaNC}$	 & $\mathrm{C_{3}S}$	 & $\mathrm{CH_{2}CN}$	 & $\mathrm{C_{5}H}$	 & $\mathrm{C_{6}H^{-}}$	 & $\mathrm{C_{7}H}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}^{13}\!CN}$	 & $\mathrm{C_{2}H_{5}NH_{2}}$ \\
			$\mathrm{OH}$	 & $\mathrm{KNC}$	 & $\mathrm{C_{3}^{34}\!S}$ $\!^{*}$	 & $\mathrm{H_{2}CCO}$	 & $\mathrm{C_{5}N^{-}}$	 & $\mathrm{CH_{2}CHCN}$	 & $\mathrm{CH_{2}ODCHO}$ $\!^{*}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	 & $\mathrm{CH_{3}C_{5}N}$ \\
			$\mathrm{SiH}$	 & $\mathrm{MgNC}$	 & $\mathrm{DNCO}$	 & $\mathrm{H_{2}NCN}$	 & $\mathrm{C_{5}S}$	 & $\mathrm{CH_{3}NCO}$, v$_{\mathrm{b}}$=0	 & $\mathrm{CH_{2}OH^{13}\!CHO}$ $\!^{*}$	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	 & $\mathrm{CH_{3}CH_{2}OCHO}$ \\
			& $\mathrm{NaCN}$	 & $\mathrm{H_{2}CS}$	 & $\mathrm{HCOCN}$	 & $\mathrm{CH_{3}OH}$	 & $\mathrm{H^{13}\!CC_{4}N}$ $\!^{*}$	 & $\mathrm{CH_{2}OHCDO}$ $\!^{*}$	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	 & $\mathrm{CH_{3}CH_{3}CO}$ \\
			& $\mathrm{SO_{2}}$	 & $\mathrm{HN^{13}\!CO}$ $\!^{*}$	 & $\mathrm{HCCNC}$	 & $\mathrm{CH_{3}SH}$	 & $\mathrm{HC_{2}^{13}\!CC_{2}N}$ $\!^{*}$	 & $\mathrm{CH_{2}CCHCN}$	 & $\mathrm{C_{8}H}$	 & $\mathrm{CH_{3}CHCH_{2}O}$ \\
			& $\mathrm{Si_{2}C}$	 & $\mathrm{HONO}$	 & $\mathrm{HNCCC}$	 & $E$-$\mathrm{HNCHCN}$	 & $\mathrm{HC_{3}^{13}\!CCN}$ $\!^{*}$	 & $\mathrm{CH_{2}CHCHO}$	& $\mathrm{CH_{2}D^{oop}CH_{2}CN}$ $\!^{*}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			& $\mathrm{SiC_{2}}$	 & $\mathrm{HSCN}$	 & $\mathrm{MgC_{3}N}$	 & $\mathrm{H_{2}CCNH}$	 & $\mathrm{HC_{4}^{13}\!CN}$ $\!^{*}$	 & $\mathrm{CH_{2}OHCHO}$	 & $\mathrm{CH_{3}^{13}\!CH_{2}^{13}\!CN}$	 & $\mathrm{HC_{11}N}$ \\
			& $\mathrm{TiO_{2}}$	 & $\mathrm{^{15}\!NH_{3}}$	 & $\mathrm{SiC_{4}}$	 & $\mathrm{MgC_{4}H}$	 & $\mathrm{HC_{4}NC}$	 & $\mathrm{CH_{3}C_{3}N}$	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{HC_{9}N}$ \\
			& 	 & $\mathrm{NH_{3}}$	 & $c$-$\mathrm{HCOOH}$	 & $\mathrm{SiH_{3}CN}$	 & $\mathrm{HC_{5}N}$	 & $\mathrm{CH_{3}COOH}$, v$_{\mathrm{t}}$=0	 & $\mathrm{CH_{3}C_{4}H}$	 & $\mathrm{NH_{2}CH_{2}CH_{2}OH}$ \\
			& 	 & $c$-$\mathrm{C_{3}H}$	 & $t$-$\mathrm{HCOSH}$	 & $Z$-$\mathrm{HNCHCN}$	 & $\mathrm{HC_{5}^{15}\!N}$ $\!^{*}$	 & $\mathrm{CHDOHCHO}$ $\!^{*}$	 & $\mathrm{CH_{3}CH_{2}CN}$	& $aGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & 	 & 	 & $l$-$\mathrm{C_{4}H_{2}}$	 & $\mathrm{HC_{5}O}$	 & $\mathrm{H_{2}C_{6}}$	 & $\mathrm{CH_{3}CH_{2}OH}$	& $gGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & 	 & 	 & $l$-$\mathrm{HC_{4}N}$	 & $\mathrm{HC^{13}\!CC_{3}N}$ $\!^{*}$	 & $\mathrm{H_{2}NCONH_{2}}$	 & $\mathrm{CH_{3}CH_{2}SH}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & $\mathrm{HOCH_{2}CN}$	 & $\mathrm{HC_{5}NH^{+}}$	 & $\mathrm{CH_{3}CHDCN}$ $\!^{*}$	 & $n$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & $\mathrm{MgC_{5}N}$	 & $\mathrm{MgC_{6}H}$	 & $\mathrm{CH_{3}OCH_{3}}$	 & $s$-$\mathrm{C_{2}H_{5}CHO}$ \\
			& 	 & 	 & 	 & 	 & $c$-$\mathrm{C_{2}H_{4}O}$	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{DC_{7}N}$	 &  \\
			& 	 & 	 & 	 & 	 & $s$-$\mathrm{H_{2}CCHOH}$	 & 	 & $\mathrm{HC_{5}^{13}\!CCN}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{HC_{7}N}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
	\vspace*{-1.5ex}
	\tablecomments{0.86\textwidth}{The prefix ``$l$-" of $\mathrm{C_{4}H_{2}}$ and $\mathrm{HC_{4}N}$ mean the C atoms are arranged in a $linear$ form, while the ``$c$-" in front of $\mathrm{C_{3}H}$ decribe a $cyclic$ form. The ``$t$-" prefix of $\mathrm{HCOSH}$ represents the two H atoms are on the opposite side of the C-S bond. $E$- and $Z$- $\mathrm{HNCHCN}$ describe the H atom and cyanyl on the same and opposite side, respectively.}
	\end{center}
\end{table}

\begin{table}[!htb]\tiny
	\begin{center}
		\caption[]{List of potentially detectable molecules in front of a bright source with one hour of integration by SKA1-mid in case 3.}
		\label{tab::all_detectable_SKA_3_absor}
		\begin{tabular}[5pt]{lllllllll}
			\hline\noalign{\smallskip}
			2 Atoms &  3 Atoms & 4 Atoms & 5 Atoms & 6 Atoms & 7 Atoms  & 8 Atoms & 9 Atoms & $>$  9 Atoms \\
			\hline\noalign{\smallskip}
			$\mathrm{KCl}$	 & $\mathrm{C_{2}S}$	 & $\mathrm{C_{3}S}$	 & $\mathrm{C_{4}H}$	 & $\mathrm{^{13}\!CH_{3}OH}$	 & $\mathrm{CH_{2}CHCN}$	 & $\mathrm{^{13}\!CH_{2}OHCHO}$ $\!^{*}$	 & $\mathrm{^{13}\!CH_{3}^{13}\!CH_{2}CN}$	 & $\mathrm{C_{2}H_{5}NCO}$ \\
			$\mathrm{OH}$	 & $\mathrm{MgNC}$	 & $\mathrm{DNCO}$	 & $\mathrm{H_{2}CCO}$	 & $\mathrm{C_{5}H}$	 & $\mathrm{H^{13}\!CC_{4}N}$ $\!^{*}$	 & $\mathrm{CH_{2}OH^{13}\!CHO}$ $\!^{*}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}^{13}\!CN}$	 & $\mathrm{CH_{3}CH_{2}OCHO}$ \\
			& $\mathrm{NaCN}$	 & $\mathrm{H_{2}CO}$	 & $\mathrm{H_{2}CNH}$	 & $\mathrm{C_{5}N^{-}}$	 & $\mathrm{HC_{2}^{13}\!CC_{2}N}$ $\!^{*}$	 & $\mathrm{CH_{2}OHCHO}$	 & $\mathrm{^{13}\!CH_{3}CH_{2}CN}$	 & $\mathrm{CH_{3}CH_{3}CO}$ \\
			& $\mathrm{SO_{2}}$	 & $\mathrm{HONO}$	 & $\mathrm{H_{2}NCN}$	 & $\mathrm{C_{5}S}$	 & $\mathrm{HC_{3}^{13}\!CCN}$ $\!^{*}$	 & $\mathrm{CH_{3}C_{3}N}$	 & $\mathrm{C_{2}H_{5}^{13}\!CN}$	 & $\mathrm{CH_{3}OCH_{2}OH}$ \\
			& $\mathrm{Si_{2}C}$	 & $\mathrm{HSCN}$	 & $\mathrm{HCOCN}$	 & $\mathrm{CH_{3}OH}$	 & $\mathrm{HC_{4}^{13}\!CN}$ $\!^{*}$	 & $\mathrm{CH_{3}COOH}$, v$_{\mathrm{t}}$=0	 & $\mathrm{C_{2}H_{5}C^{15}\!N}$	 & $\mathrm{HC_{9}N}$ \\
			& $\mathrm{SiC_{2}}$	 & $\mathrm{^{15}\!NH_{3}}$	 & $\mathrm{MgC_{3}N}$	 & $\mathrm{H_{2}CCNH}$	 & $\mathrm{HC_{5}N}$	 & $\mathrm{H_{2}C_{6}}$	 & $\mathrm{C_{8}H}$	& $aGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& $\mathrm{TiO_{2}}$	 & $\mathrm{NH_{2}D}$	 & $\mathrm{SiC_{4}}$	 & $\mathrm{MgC_{4}H}$	 & $\mathrm{HC^{13}\!CC_{3}N}$ $\!^{*}$	 & $\mathrm{H_{2}NCONH_{2}}$	& $\mathrm{CH_{2}D^{oop}CH_{2}CN}$ $\!^{*}$	& $gGg'$-$\mathrm{(CH_{2}OH)_{2}}$ \\
			& 	 & $\mathrm{NH_{3}}$	 & 	 & $Z$-$\mathrm{HNCHCN}$	 & $\mathrm{MgC_{5}N}$	 & $\mathrm{MgC_{6}H}$	 & $\mathrm{CH_{3}^{13}\!CH_{2}^{13}\!CN}$	 & $i$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & $l$-$\mathrm{C_{4}H_{2}}$	 & $c$-$\mathrm{C_{2}H_{4}O}$	 & $\mathrm{NH_{2}CH_{2}CN}$	 & $\mathrm{CH_{3}^{13}\!CH_{2}CN}$	 & $n$-$\mathrm{C_{3}H_{7}CN}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}CN}$	 & $s$-$\mathrm{C_{2}H_{5}CHO}$ \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}OH}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CH_{2}SH}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}CHDCN}$ $\!^{*}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{CH_{3}OCH_{3}}$	 &  \\
			& 	 & 	 & 	 & 	 & 	 & 	 & $\mathrm{HC_{7}N}$	 &  \\
			\noalign{\smallskip}\hline
		\end{tabular}
	\end{center}
\end{table}

Figure \ref{fig::absorb_gly_ala_SKA} shows the detectability of glycine and alanine. We already discussed in Sec. \ref{sec::SKA_prebiotic} that glycine and alanine have the potential to be detected by SAK1-mid via their emission lines in a reasonable time. Under our  assumptions, their absorption lines are even easier to detect when the excitation temperatures are low ($\lesssim$10\,K): it would take 10 hr for SKA1-mid to detect glycine/alanine even if the column density is as low as $7\times10^{12}$/$2\times10^{13}$\,cm$^{-2}$.

\begin{figure}[!htb]
	\centering
	\includegraphics[width=14cm]{pics/ms2022-0236fig13.pdf}
	\vspace{-4mm}

	\includegraphics[width=14cm]{pics/ms2022-0236fig14.pdf}
	\caption{Integration time requirement for SKA1-mid to observe the absorption lines of glycine  (\emph{top}) and alaline (\emph{bottom}) for $T_{\text{bg}}=200$\,K and $\theta_{\text{bg}}=0.5$\,$''$.}
	\label{fig::absorb_gly_ala_SKA}
\end{figure}

\section{Conclusion}
\label{sec::conclusion}

Molecular spectroscopic data are at the base of the molecule identification process. A meta-analysis of related databases gives us a clue about the prospects of future detection of interstellar molecules. The main results of this paper are as follows:
\begin{itemize}
	\item [1)]
	Most transitions in CDMS and JPL reside in 100$-$1000\,GHz. Transitions within 10$-$1000\,GHz mostly have low frequency uncertainties, and most transitions with high frequency uncertainties are faint (hence unimportant anyway).
	\item [2)]
	Under some common assumptions, the frequency concentration between 100 and 1000\,GHz makes this range more likely to suffer from line confusion problems, causing it more difficult to confirm a molecular species in this frequency range.
	\item [3)]
	More simple molecules can be detected by the HSTDM onboard CSST, while SKA1-mid can detect more complex molecules with one-hour of observation in a variety of ISM environments. Due to the narrow frequency coverage by far, only OH and $\mathrm{^{13}\!CH_{3}OH}$ can possibly be observed by FAST in one hour with plausible assumptions on their column densities.
	\item [4)]
	Prebiotic molecules such as glycine with a column density of ${\sim}1 \times 10^{15}$\,cm$^{-2}$ can be detected by CSST/HSTDM in a 10 hr; SKA1-mid is able to detect glycine and alanine with $N_{\mathrm{tot}}\gtrsim 1 \times 10^{15}$\,cm$^{-2}$ and  $T_{\mathrm{ex}}\simeq 35$\,K in 10 hr. Several strong lines of them are likely not blended by the lines of other molecules hence are ideal for the identification of these molecules.
	\item [5)]
	How a bright background source influences the detectability of molecules depends on its angular size and brightness temperature. For SKA1-mid, the introduction of a bright background source behind a cold dense molecular cloud makes prebiotic molecules easier to detect via absorption features. Compared with emission, glycine/alanine with column densities as low as $7\times10^{12}$/$2\times10^{13}$\,cm$^{-2}$ are able to be detected by SKA1-mid by absorption in 10 hr under our assumptions. Because of the extremely small filling factor, the compact background source has little influence on the detectability of molecules while using CSST/HSTDM and FAST.
	\item [6)]
	When discussing the line confusion problem and detectable molecules in one hour, we simply set the excitation temperature and velocity width of previously identified molecules to the same typical value, respectively, and the column densities of these molecules to their literature or empirical values. These assumptions are oversimplified because the physical parameters may vary dramatically under different interstellar environments. Besides, only one velocity component is considered for each source, which surely underestimate the line confusion problem in crowded regions. When talking about the detectability of prebiotic molecules, the velocity width is fixed to a constant. In the future we will investigate ways to predict the detectability of molecules more realistically.
\end{itemize}

\begin{acknowledgements}
	We thank the referee for his/her constructive suggestions which help to improve the quality of the paper. This work is financially supported by the National Natural Science Foundation of China through grants 12041305 and 11873094, and by the China Manned Space Project.
\end{acknowledgements}

\bibliographystyle{raa}

redpajama_set_name: RedPajamaArXiv


White bean salad is probably one of the healthier Italian dishes to eat. It is ridiculously easy to make, and doesn't require any actual cooking at all. The ingredients are simple and not very difficult to obtain; you probably have most of them in your kitchen already. Once you have the proper ingredients, you really just need to toss them together in the portions most suitable to your taste, and presto, you have a wonderful salad that can be eaten as an appetizer or main course.
This white bean salad's main ingredient are cannellini beans. These little guys are packed full of protein which is why they work so well as a vegetarian meat substitute. Eating sufficient quantities of protein is important because protein helps the body build and maintain cells. It also helps with muscle fatigue and muscle tissue damage recovery, which is perfect for weight lifters and physically active people who need to recover from their fatigue quickly.
Stir together the beans, artichokes, olives, peppers, cucumber, tomatoes, celery and green onions in a large bowl.
Whisk together the vinegar, Dijon mustard, parsley, thyme, rosemary, garlic powder, paprika, salt, and pepper in a small bowl.
Gradually pour in olive oil until well combined.
Pour the dressing over the salad, and stir until all ingredients are coated.
Refrigerate at least one hour or overnight before serving.
The flatulence producing effect of beans is caused by oligosaccharides, a type of sugar molecule.


text:
Christine Jane M. Gonzalez
DOST launches first Nat'l research agenda for mental health
The country's lead in health research, Department of Science and Technology – Philippine Council for Health Research and Development (DOST-PCHRD), announced the conception of the first National Mental Health Research Agenda (NMHRA) during the World Mental Health Week on Friday, October 11, 2019 at the Philippine International Convention Center, Pasay City.
Intended to set direction for the country's future mental health research investments, the development of NMHRA 2019-2022 was facilitated by DOST-PCHRD and the World Association for Psychosocial Rehabilitation (WAPR) – Philippines, working with various stakeholders. The selection of NMHRA research priority areas is based on the provisions of the Philippine Mental Health Act of 2017.
"We still have much to do in the field of mental health research, and I hope with the NMHRA, we can inspire more evidence-informed research programs on mental health in the country," said Dr. Jaime C. Montoya, Executive Director of DOST-PCHRD.
According to the Principal Investigator of NMHRA and the President of WAPR-Philippines, Ms. Lucita Lazo, mental health is not a national priority over the years, but now solutions to address the problems are being brought out. Ms. Lazo expressed her high hopes that more government and non-government organizations will initiate and support mental health research efforts in the country.
Ms. Lazo co-developed the NMHRA with Dr. Lourdes L. Ignacio, the Founding President of WAPR-Philippines.
Mental health situation in the Philippines
"In a developing country like the Philippines, the shortage of human and financial resources along with the stigma on anything "mental", and the low prioritization for mental health hamper the national capacity to respond to the increasing needs of the Filipino to sustain a good quality of life," said Dr. Ignacio.
Mental health is listed as the third most prevalent form of illness in the Philippines (Lally et. al., 2018). The Department of Health reported that one in every five Filipino adults has some form of mental illness.
Every year, around 3,500 Filipinos commit suicide (World Population Review, 2019). Additionally, the highest percentage of depression affects teenagers and young adults aged 16 to 29.
In terms of healthcare, there are only 2-3 mental health workers for every 100, 000 Filipinos (World Health Organization and DOH, 2006). This, according to experts, accounts for a severe shortage of mental health specialists in the country. Moreover, researchers argue that mental health in the Philippines remains an under-resourced aspect in healthcare.
National developments in mental health
According to Dr. Ignacio, there are two major waves of mental health development in the Philippines. The first was initiated in 2001 by the National Mental Health Policy issued by the Secretary of Health as the country's commitment in observance of the World Health Day. The second was done in the last two years: the enactment of the Philippine Mental Health Act of 2017, the promulgation of its implementing rules and regulations, and the enactment of the Universal Health Law. These recent developments are all deemed to change the landscape of mental health in the country.
The future of mental health research with NMHRA 2019-2022
Mental health is one of the research priorities in the National Unified Health Research Agenda (NUHRA) 2017-2020. However, no mental health research framework existed which the DOST-PCHRD could follow in supporting mental health programs.
With the NMHRA 2019-2022, future mental health research projects are expected to achieve three major outcomes as follows: improved mental health information system; strengthened leadership and governance; and accessible, available, affordable, and responsive mental health services.
According to Ms. Lazo and Dr. Ignacio, a strengthened mental health information system is crucial as it will lay the basis for innovations in the field. More so, this will help steer the provision of mental healthcare services for Filipinos. Subsequently, an improved leadership and governance will ensure adequate supply of resources needed for mental health services in the country. Well-informed duty bearers will fuel the provision of treatment and care in local mental health facilities and mental hospitals, which will increase the availability of mental health services among local communities all over the country.
The new mental health research agenda seeks to support the current policy reforms in mental health, as it is informed by developments at the global level and continues to support a life course perspective on mental health research.
"Now, it seems like there can be reality to the movement towards approaching mental health from a transformative framework to being more wide-ranging, as it's going to traverse the whole of life, because that's what mental health is all about, the whole total well-being, so exciting!" Dr. Violeta Bautista, head of UP Diliman's Clinical Psychology Program stressed.
PCHRD News

redpajama_set_name: RedPajamaCommonCrawl


If you are one of those people then this article is for you. This article is Search Engine Optimisation for beginners and is a great guide if you aren't sure where to start with SEO.
So what is Search Engine Optimisation?
It is the process used for getting your website ready for Google. If you run a business then you can't afford to ignore Google (the number one search engine globally).
There are two ways for your website to appear in Google. One is through paid advertising like adwords and the second is through the natural search results.
The ads appear at the top and in the sidebar and they show the icon AD next to them. This indicates that the company are paying for that ad spot.
The ones that are further down are the natural results and Google organises these results based on relevance. Basically you are going to be showing Google that you are relevant for your business topic or keyword.
The aim of the game is to get onto the first page of the search results. Those companies who are take the top spot generate a huge amount of traffic to their website.
I know that might all sounds confusing but I promise by the end of the article it will all make more sense. SEO doesn't have to be complicated and it just takes a little thought and common sense.
One of the most crucial parts of your Search Engine Optimisation work is your keyword research. It is one of the biggest things we work on when we start on an SEO campaign.
However, it doesn't have to be that complicated – a little common sense and your website can be ranking up with the best of them.
Ideally what you want to do is choose one keyword per page.
1. The first think you need is a Google account. If you don't have one then follow this tutorial.
2. Sign into Google Adwords with your Google account. You want to use the keyword planner tool.
4. If you are an accountant in Sydney you would put that into the product/service area, along with filling in the rest of the information.
5. Once you click the Get Ideas then it will bring up the Keyword Ideas relevant to your business search.
6. You want to short list keyword ideas that you ideally would like to rank for. These will become the basis for the on page SEO you will do.
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Choose longer keywords rather than a one word keyword. For example tax accountant sydney cbd is much better than the simple 'accountant'. The longer the keyword the less competition, which means you will rank easier than the higher competition words.
Ideally you want to focus on one keyword per page, this is the recommended technique from Google.
Before you begin this work I recommend installing the Yoast SEO plugin for WordPress to your website.
Input your keyword into the focus keyword section. Remember we only want to focus on one keyword per page.
Then I want you to review your wording throughout the page, are there places where you can input your keyword strategically? The key to this is to ensure the wording reads well and don't put it in too many times. Google looks for this and will penalise if you use the word too much.
Quite simply meta-tags are the things that tells Google what your page is about.
You can tell Google exactly what you want this to say by editing your meta-tags. If you are using WordPress you will need to have the Yoast SEO plugin for WordPress installed on your website.
For each of your pages you want to choose one of your keywords to focus on. To edit your meta-tag you can edit your page then scroll down to your Yoast settings.
You want to ensure you put your keyword your SEO Title section (this is the most important). This is how you will tell Google about your page.
You can then complete your Meta description with some wording on what the page is about, write this with people in mind rather than Google but it is a great idea to include your keyword again.
See my example for this page.
1. Do your keyword research and choose the keywords relevant to your business/website/pages on your site.
2. Go through each of those pages and edit your content (wording) so that you are using your keyword. Remember go with one keyword per page.
3. Set up your meta-tags on each page whilst you are there to match your keyword.
Download our keyword template so you can track your pages and keywords.
Look out next week for more tips on SEO for your business.
If you need help with your Search Engine Optimisation then send us an email to see how we can help you.


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"It works on principles I really admire in games and in life"
Why I Love: Ghost Town Games' Phil Duncan writes about Storage Inc., the Xbox Live Indie Game that influenced Overcooked
Opinion by Phil Duncan Contributor
Why I Love is a series of guest editorials on GamesIndustry.biz intended to showcase the ways in which game developers appreciate each other's work. This installment was contributed by Phil Duncan, co-founder of Ghost Town Games, creator of the BAFTA-winning cooperative multiplayer game Overcooked.
I've always been drawn towards cooperative games. When my dad bought me and my brothers a Mega Drive back in the early '90s I remember the frustration whenever I'd have to compete with my older siblings. I was always much more drawn to games we got to play together: Streets of Rage, Golden Axe, ToeJam & Earl... Hell, I'd even tag in as Tails in Sonic 2 if it meant I didn't have to get my butt whupped in Street Fighter again.
There's something about that shared experience of tackling a game together that really stuck with me, and it's something I've enjoyed in games ever since. When I used to work at Frontier Developments, my friends and I would meet at lunch times to play whatever local multiplayer games we could get our hands on but were similarly drawn to games we could team up to play, games where we worked together towards a common goal.
Storage Inc. was a strange little find, a downloadable indie game on the Xbox 360 created by solo developer Stolpskott Studios, which saw players take control of forklift trucks in order to ferry boxes of unknown content around a series of differently laid out warehouses. As new boxes arrived you need to organise them in the warehouse while simultaneously looking to ship out the older boxes, all while trying not to block each other in or get in each other's way. It was a deceptively simple premise, one which really sparked something in our group and which influenced Overcooked in a number of different ways.
The physicality of the game was one of the things that really stood out. This was a game where the dimensions of your avatar really mattered, where you could influence the outcome of the game simply by being positioned in the wrong place. You had to be aware of your surroundings constantly so all players could access the boxes they needed. You were forever having to back out of corridors to allow an incoming player to pass or participate in that awkward left/right shuffle as you try to negotiate your way past another player. There was a real sense of being in the space and it led to a lot of hilarity and frustration in equal measure--a lot more of the latter if playing with the wrong kind of troll. :-)
Storage Inc. is a game about cooperation, and getting in each other's way
The other thing it revealed was a need for good communication, this was a co-operative game where you couldn't simply carry out your own agenda in silence, you'd quickly find yourself heading to a box only to have it snaffled away by your teammate. A lot of the joy came in trying to quickly articulate your intentions as you careened around the stage in your tiny forklift desperately trying to ferry your box to the delivery zone. What I remember really being drawn to was how much the game changed depending on who you were playing with; the best teams were always those who could communicate well and wouldn't fly off the handle. The real game seemed to be much more in the interaction between the players than what was necessarily happening on screen.
Finally, I liked the fact the game didn't have an enemy as such, just a benevolent hatch delivering differently labelled boxes one after the other, your common goal to survive as long as you could against the waves of deliveries as the warehouse gradually filled up with more and more obstacles for you and your teammates to negotiate. In Storage Inc., you don't succeed or fail as an individual, you do it as a team. It's not a game where one person can be so good at it they can carry the others. Your success depends on the strength of each member working together.
It's not the most aesthetically pleasing game, and there are some odd choices in the game's design which can at times leave it feeling more frustrating than fun, but what I love about Storage Inc. is that it works on principles I really admire in games and in life. You get to experience first hand the challenges, the frustrations, and ultimately the sense of satisfaction when you succeed as a team. It's the little moments: where you realise it's quicker to pass a box to a friend than trying to bully your way past to do it yourself, a sense that working as a team is not only easier than working alone but also more rewarding.
Overcooked was very much influenced by games like Storage Inc. Oli [De-Vine, the other half of Ghost Town Games] and I both love games which bring people together and encourage them to think or act in ways other games might not. It sounds cheesy but I wish more games would embrace the spirit of cooperation and communication in the same fashion, so that more gamers get to share in the same experiences I've enjoyed so much over the years.
Upcoming Why I Love columns:
Tuesday, October 10 - Dizzy creators The Oliver Twins on the BBC Micro
Tuesday, October 24 - Yooka-Laylee's Gavin Price on Super Mario Kart
Tuesday, November 7 - Wasteland 3's Brian Fargo on Inside
Tuesday, November 21 - Voyageur's Bruno Dias on Magic: The Gathering
Developers interested in contributing their own Why I Love column are encouraged to reach out to us at news@gamesindustry.biz.
Why I Love
Phil Duncan
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home > press reports > daily news > daily news - 6 august 1888
MR. RICHARD MANSFIELD AT THE LYCEUM
After much manoeuvring and counter manoeuvring, Mr. Richard Mansfield has succeeded in outdistancing his rival, Mr. Bandmann, and has presented himself to the English public in a version of the "Strange Case of Dr. Jekyll and Mr. Hyde" a good forty eight hours before anybody else. This effort, which for a moment seemed likely to be baffled by the astuteness and fertile resource of his antagonist, may be of good omen. The demand for dramatic versions of Mr. Stevenson's fascinating little story cannot be supposed at this dull period of the dramatic calendar to be at fever height; and it is more then possible that two Jekylls and two Hydes may prove ot be in excess of the public requirements. If so, there is a manifest advantage in being first in the field. Apart from this, the sympathy of playgoers is attracted to the Lyceum piece by more than one influence. Nobody appears to have discovered any dramatic capabilities in this narrative till Mr. Mansfield saw, or believed he saw, in it a good vehicle for his talents; and having induced his friend, Mr. Russell Sullivan, the American playwright, to prepare it for the stage, with the sanction of the original author, brought it out at Boston, and subsequently in New York, with brilliant success. Mr. Mansfield has thus acquired the sort of claim that attaches to priority of possession. A more fortunate circumstance for him still is that English playgoers, as was abundantly testified by the aspect of the Lyceum Theatre at the rising of the curtain on Saturday, are curious about Mr. Mansfield. He left us some seven or eight years ago an obscure young actor; he has returned with a great renown. In America his doings excite and interest second only to those of Mr. Irving when he happens to be on that side of the Atlantic; and though the present piece is not that in which he gained his high reputation, it has given rise to no little discussion and is considered by his American admirers to exhibit a new phase of his powers.
Mr. Mansfield's first entrance on the stage on Saturday caused some surprise, and, we are bound to add, some shade of disappointment. The spectators were not prepared to find the grave and stately Jekyll transformed into a young gentleman of slight stature and of somewhat insignificant appearance. But the adapter has judged it imperatively necessary to introduce what is called "a love interest" into the sombre story of the doctor and his evil double; and this preliminary settled, there was nothing left but to make Jekyll the enamoured and necessarily youthful swain. The price paid for this departure is doubly heavy; for the love making between Jekyll and the daughter with whom it has pleased the dramatist to endow Sir Danvers Carew does not stir the pulses; and the tones, gestures, and movements of Miss Beatrice Cameron were unfortunately of a nature to make the spectator sigh for one touch of truth and spontaneous impulse. It was the sudden appearance of the terrible Hyde towards the close of this scene and the murderous attack upon Sir Danvers that struck the imaginative keynote and brought the whole house to that mood of silent attention which is the crowning evidence of the actor's power. But a moment had passed since Jekyll had left the terrace by the drawing room windows when this strange creature reappeared, bent and twisted of form, with odd contortions of the hands and stealthy, tiger like movements, hissing out words of scorn and defiance. The change appears to be accomplished without mechanical aids beyond some touches that give a repulsive pallor to the features, and some sudden manipulation of the eyes which completes the sinister aspect of this embodiment of evil. The wigmaker's art, which is potent on these occasions, played no part, for Mr. Mansfield wore throughout his own hair. As much as to anything else, the chill of terror felt by the spectator was attributable to the fierce, raucous tones of the monster as he shouted with devilish glee, clawing at his victim's breast and trampling him under foot "with apelike fury" as the story says. The subsequent changes from Jekyll to Hyde were still more impressive, and were for the most part effected on a half darkened stage in full view of the spectator. Whenever Mr. Mansfield becomes Hyde, his savage chuckles, his devilish gloating over evil, his malignant sarcasms, his fierce energy of hate and revelling in all sinful impulses awaken strange sensations in the spectator; and the unearthly restless figure of this variation upon Frankenstein's fatal handiwork takes a powerful hold on the imagination.
Hyde, in brief, in Mr. Mansfield's hands is a creation of genius. There is little more to be said. We do not quite understand the notion that the adaptor has improved on Mr. Stevenson by exhibiting Jekyll as constantly haunted with a horror of the crimes of his other self. Surely this is the position in the story - at all events in the later stages. Mr. Mansfield's fits of remorse are the least effective passages in the play. They are spun out in the final scene to such an unconscionable tenuity that it is hard to avoid a suspicion that they are introduced from a sheer lack of anything else wherewith to fill the last act. the story, as presented on the stage, is, to tell the truth, neither very clear nor in itself very interesting. The attempts to heighten its gloom by the ravings of Hyde's servant Rebecca Moor - a sort of sublimated and aged Rosa Dartle, and again to correct its sombre tendencies by the jocularities of Inspector Newcomen, are equally unhappy. It is, if we remember rightly, this official who talks of "tanning the Hyde" as if he were an inspector in one of Mr. Burnand's burlesque parodies. His appearance is certainly responsible for Jekyll's ill timed exclamation "Ha! an inspector of police!" which approaches perilously near to the ludicrous in the very crisis of the play. The town will doubtless flock to see Mr. Mansfield's "dual impersonation"; but it is to be hoped that we shall ere long have an opportunity of seeing him as the Baron in "A Parisian Romance", a part which first made him famous.
MADAME TUSSAUD'S EXHIBITION
Madame Tussaud and Sons are putting forth an extensive programme for the Bank Holiday, when they usually receive many hundreds of excursionists. A portrait of the present Emperor of Germany will be shown in the Great Hall, near to the imposing group portraying the lying in state of the late Emperor William. It should be mentioned that this group also contains artists' models of the ever remembered Emperor Frederick and of the great Chancellor. the Chamber of Horrors also is interesting, as containing the model of the notorious Jackson and of the many criminals who have marked the year. During the holiday week the orchestra will be greatly strengthened.
Dissertations: The Strange Case of Dr Jekyll and Saucy Jacky
Message Boards: Richard Mansfield
Press Reports: Atchison Daily Globe - 16 September 1887
Press Reports: Atchison Daily Globe - 20 July 1888
Press Reports: Echo - 13 August 1888
Press Reports: Marion Daily Star - 11 June 1887
Press Reports: Morning Advertiser - 7 August 1888
Press Reports: Pall Mall Gazette - 8 September 1888
Press Reports: Star - 18 September 1888
Press Reports: Times [London] - 6 August 1888
Ripper Media: Jack the Ripper: A Suspect Guide - Richard Mansfield


Common sense prevails. Now we'll be able to tighten a screw or fix something with pliers while traveling.
A mountain man soon will be able to take one of his most indispensable possessions — a Leatherman or Swiss Army knife — with him when he travels by air.
The Transportation Security Administration announced yesterday that it will permit passengers to carry pocket knives on flights beginning April 25. The long-overdue change will allow knives with blades no more than 2.36 inches long (6 cm) and a half-inch wide.
According to ABC, the TSA confiscated tens of millions of pocket knives from flyers since 2001 — a gigantic waste and source of immeasurable aggravation.
Ski poles, golf clubs and hockey and pool sticks also will be allowed on flights under the new regulations.
Air travel just got a little less maddening. Except, of course, for longer security lines due to the sequester.
… of course, you still can't carry liquids or gels more than 3 ounces. So don't try and sneak on a flight with a regular sized tube of toothpaste or some shampoo!!
The knife pictured doesn't qualify. The blade is too long. Only the Keychain group of tools from Leatherman meet the specs. Also there are only 3 knives in the Wenger catalog that meet the specs and they are all three the tiny little Swiss Army Knives that have the tiny pen blade, the nail file and the tiny little scissors. I'm glad they are finally allowing some form of knife so that I can more easily open that peanut pouch but my regular pocket knife is still going to have to go into the checked luggage.
My Leatherman Juice (pictured) does meet the requirements, barely. Assuming blade means only the sharpened part.
Blade length means the entire blade. Not just the sharpened part. I had that discussion with some other folks on another forum and they found the TSA reg.
Says 2.36″ or 6cm from tip to where it meets the handle.
if you are going to assume anything about this and the TSA in general, I would think you should err on the conservative side and place your beloved knife in the checked bags.
I believe Larry is right, blade length can be considered 'stabbing depth'…not sharpend edge length.
I plan to shorten the blade on my Juice down to the 6cm in order to meet the maximum length. I really like the tool and often do not check a bag.


Starting and running a note business is an exciting prospect because it is an opportunity to be your own boss and run your own small business. It is important to realize, however, that being your own boss also creates new challenges, such as standing on your own two feet and fending for yourself. It is like leaving home for the first time – there are many risks and uncertainties, but also opportunities: big rewards, a sense of achievement and peer recognition.
The wise entrepreneur has chosen the note business because he or she knows what kind of work they do best and it is a field in which he or she is interested in (real estate). The greater the individual's passion and enjoyment, the greater chance of success in the note business. In addition to technical expertise and product knowledge of the note business, it may also be necessary to be able to manage cash-flow, accounting, budgets, bookkeeping and taxes. Having chosen the wonderful niche of seller financed notes the individual now needs to acquire some skills including marketing, negotiating, phone skills, calculator skills and (what this article is about) business management skills.
Individuals in the note business are absolutely entrepreneurs. Entrepreneurs spot opportunities and organize resources to create their own businesses. They have the vision, business skills and courage to take risks and possess the necessary leadership qualities to overcome problems. Entrepreneurs normally have a strong internal control (their destiny and success are determined by their own actions), self-confidence, passion, determination and the management skills to plan and control the process.
Just like any other business, Note Business entrepreneurs have to manage with management being defined as the process of ensuring that the business achieves its goals and objectives. Note business management, as in any small business, is essentially the management of your note business on a day-to-day basis, which includes activities in functional areas, such as marketing, production, finance and building your team.
1. Planning – Adequate planning is needed – in the long, medium and short term. Good note business management includes goals and a written plan of attack. That will include a Marketing Plan and a Business Plan. I've written plenty of articles about both (I provided a template in a previous article) and encourage you to take a day out of your life, sit down and really think about what your short (6-12 months), medium (2-3 years) and long range (5-10 years) goals and plans are exactly. When we have a clearly defined plan with goals, milestones and benchmark's it makes accomplishing them that much easier, even if we do not quite accomplish all of them, we will get much closer to them by having them in writing. Planning also includes having a daily, weekly and monthly schedule of routine tasks and duties (see Organization).
2. Organizing – This means making decisions on how to divide up the work that is to be completed. Good note business management includes good organization and good organization is a learned skill that includes time and priority management, both personal and professional. If you do not practice good time and priority management in your personal life how do you expect to have it in your note business? For Time Management: eliminate unnecessary tasks, make lists, focus, take breaks and identify your productive times. On Priority Management, do this… goggle "The Eisenhower Box", I've been using this as long as I can remember. Dwight Eisenhower, 34th President of the United States said it best, "What is important is seldom urgent and what is urgent is seldom important." He explains it in diagram form using important and urgent as the scales. Everything you do every day can be put into four categories including 1 – Have to do's (things that are important and urgent) 2 – Need to do's (things that are important and not urgent) 3 – Want to do's (things that are not important but urgent) and 4 – Wish to do's (things that are not important and not urgent). By looking at the things you do on a daily basis and putting them into these four categories it will help you prioritize your tasks in an efficient manner which in turn helps you manage your time. There is also something to be said for getting things done through other people (your team) who we may be able to delegate some of the things that we do not necessarily have to do ourselves (licking, stuffing and stamping envelopes, processing, taxes, etc.).
3. Leadership – This involves the effective supervision and motivation of you and your team. Leadership is a vast topic yet so very fundamental to note business management. Even if you are a one man operation demonstrating leadership characteristics is a developed skill everyone can acquire. It includes among many other things: good communication skills (clear and direct, using open ended questions), listening skills (actually listening not just hearing;, restating, reframing and rephrasing questions), decisiveness and knowing what motivates you and your team members (not everything motivates everyone). Do yourself a favor and read the book Think and Grow Rich by Napoleon Hill or at a minimum google "21 PRINCIPLES OF LEADERSHIP FROM NAPOLEON HILL". That includes his 11 major attributes of leadership AND 10 major causes of failure in leadership. It can be very enlightening.
4. Control – This includes monitoring performance, in other words, comparing what should have been done with what was really done. Corrective action should be considered if a gap is found to exist in your note business. This ties in directly with time and priority management, having control over your time and priorities. In addition, tracking your marketing, keeping statistics and having a paper trail (both online in emails and off line in a file cabinet) for all communications and transactions. It also means having emotional self-control, being professional, keeping a positive attitude and eliminating negativity.
Each of the above management activities can be an article, book or workshop in itself. The idea is to be highly aware of what these note business fundamental business management activities are and to begin incorporating them into your note business on a daily, weekly, monthly and yearly basis. An important focus area of effective note business management (and self-management) is getting things done through other people, not doing everything yourself and to ensure that tasks are accomplished and that note holders, investors and your team are satisfied.
The article is enlightening.- Business Management and the Note business.. I enjoy the four fundamental business actions. They are great skills to have. TWITA!!!