Discovery of fulvenallene in TMC-1 with the QUIJOTE line survey

We report the detection of fulvenallene ($c$-C$_5$H$_4$CCH$_2$) in the direction of TMC-1 with the QUIJOTE line survey. Thirty rotational transitions with $K_a$=0,1,2,3 and $J$=9-15 were detected. The best rotational temperature fitting of the data is 9\,K and a derived column density is (2.7$\pm$0.3)$\times$10$^{12}$ cm$^{-2}$, which is only a factor of 4.4 below that of its potential precursor cyclopentadiene ($c$-C$_5$H$_6$), and 1.4--1.9 times higher than that of the ethynyl derivatives of cyclopentadiene. We searched for fulvene ($c$-C$_5$H$_4$CH$_2$), a CH$_2$ derivative of cyclopentadiene, for which we derive a 3$\sigma$ upper limit to its column density of (3.5$\pm$0.5)$\times$10$^{12}$ cm$^{-2}$. Upper limits were also obtained for toluene (C$_6$H$_5$CH$_3$) and styrene (C$_6$H$_5$C$_2$H$_3$), the methyl and vinyl derivatives of benzene. Fulvenallene and ethynyl cyclopentadiene are likely formed in the reaction between cyclopentadiene ($c$-C$_5$H$_6$) and the ehtynyl radical (CCH). However, the bottom-up gas-phase synthesis of cycles in TMC-1 underestimates the abundance of cyclopentadiene by two orders of magnitude, which strengthens the need to study all possible chemical pathways to cyclisation in cold dark cloud environments, such as TMC-1. However, the inclusion of the reaction between C$_3$H$_3^+$ and C$_2$H$_4$ produces a good agreement between model and observed abundances.


Introduction
The QUIJOTE 1 line survey of TMC-1 (Cernicharo et al., 2021a) performed with the Yebes 40m radio telescope has permitted the detection of nearly 40 new molecular species in recent months, most of which are hydrocarbons and cycles such as indene, benzyne, cyclopentadiene, and two isomers of ethynyl cyclopentadiene (see e.g. Cernicharo et al. 2021a,b,c,d,e and references therein). Propargyl (CH 2 CCH) has been found to be one of the most abundant hydrocarbon radicals in this source (Agúndez et al., 2021. Other hydrocarbons such as ethynylallene (CH 2 CCHCCH), vinylacetylene (CH 2 CHCCH), and butadiynylallene (CH 2 CCHC 4 H) have also been found to have high abundances (Cernicharo et al., 2021b,d;Fuentetaja et al., 2022). Moreover, cyano derivatives of benzene and naphthalene have also been found towards TMC-1 (McGuire et al., 2018. This suggests that benzene and naphthalene are also very abundant in this cold prestellar core. To understand the formation of these species in the gas-phase, and their large abundances (see Appendix A), we have to consider very fast reactions between a few precursors. It is possible, however, that some gas-phase chemical reactions are still missing in the chemical networks. It is also likely that important hydrocarbons with low dipole moments are still awaiting detection. Hence, discovering new hy-Based on observations carried out with the Yebes 40m telescope (projects 19A003, 20A014, 20D023, and 21A011). The 40m radiotelescope at Yebes Observatory is operated by the Spanish Geographic Institute (IGN, Ministerio de Transportes, Movilidad y Agenda Urbana). 1 Q-band Ultrasensitive Inspection Journey to the Obscure TMC-1 Environment drocarbons through sensitive line surveys will certainly help in getting a complete chemical network (gas-phase and dust surface reactions) to explain the chemistry of hydrocarbons and polycyclic aromatic hydrocarbons (PAHs) in TMC-1.
In this letter we report the discovery of fulvenallene (c-C 5 H 4 CCH 2 ) through the detection of 30 rotational transitions in the frequency range 31-50 GHz. The structure of fulvenallene (c-C 5 H 4 CCH 2 ), an isomer of ethynyl cyclopentadiene, is shown in Fig. 1. We discuss the chemistry of this hydrocarbon cycle in the context of a bottom-up gas-phase scheme for the formation of hydrocarbon cycles in TMC-1.

Observations
New receivers built within the Nanocosmos project 2 , and installed at the Yebes 40m radiotelescope, were used for the observations of TMC-1 (α J2000 = 4 h 41 m 41.9 s and δ J2000 = +25 • 41 27.0 ). A detailed description of the system is given by Tercero et al. (2021). Details of the QUIJOTE line survey are provided by Cernicharo et al. (2021a). The observations were carried out during different observing runs between November 2019 and May 2022. The receiver consists of two cold high electron mobility transistor amplifiers covering the 31.0-50.3 GHz band with horizontal and vertical polarisations. Receiver temperatures in the runs achieved during 2020 vary from 22 K at 32 GHz to 42 K at 50 GHz. Some power adaptation in the down-conversion chains reduced the receiver temperatures during 2021 to 16 K at 32 GHz and 25 K at 50 GHz. The backends are 2 × 8 × 2.5 GHz fast Fourier transform spectrometers with a spectral resolution of 38.15 kHz providing the whole coverage of the Q band in each polarisation.
The data presented here correspond to 546 hours of observing time on the source, of which 293 and 253 hours were acquired with a frequency switching throw of 8 MHz and 10 MHz, respectively. The data analysis procedure is described in Appendix B. The intensity scale used in this work, antenna temperature (T * A ), was calibrated using two absorbers at different temperatures and the atmospheric transmission model ATM (Cernicharo, 1985;Pardo et al., 2001). The antenna temperature has an estimated uncertainty of 10 % and can be converted to main beam brightness temperature, T mb , by dividing by B eff /F eff . For the Yebes 40m telescope, B eff = 0.738 exp[−(ν(GHz)/72.2) 2 ] and F eff = 0.97 (Tercero et al., 2021). All data were analysed using the GILDAS package 3 .

Results
QUIJOTE has now reached a level of sensitivity (0.1-0.3 mK per 38.15 kHz channel across the Q band) that permits the detection of new isotopologues and derivatives of abundant species. Examples of detection and complete spectral characterisation of rare isotopologues through QUIJOTE data are HDCCN (Cabezas et al. , 2021a), CH 2 DC 3 N , and CH 2 DC 4 H (Cabezas et al. , 2022a). Although QUIJOTE has not yet reached the confusion limit, special care should be taken when assigning lines to a given molecule as blending with other features often occurs. Line identification in this work was done using the following catalogues: MADEX (Cernicharo, 2012), CDMS (Müller et al., 2005), and JPL (Pickett et al., 1998). By May 2022 the MADEX catalogue had 6434 spectral entries corresponding to the ground state and vibrationally excited state, together with the corresponding isotopologues, of 1734 molecules.
Rotational spectroscopy of fulvenallene was performed in the laboratory by Sakaizumi et al. (1993) up to frequencies of 39.3 GHz with an accuracy of 50 kHz, and by McCarthy et al. (2020) up to frequencies of 25 GHz with an accuracy of 2 kHz. To search for fulvanellene in TMC-1 we fitted these data, but discarded the less accurate measurements of Sakaizumi et al. (1993), which are also present in the data set of McCarthy et al. (2020). The derived rotational and distortion constants are shown in the middle column of Table 1, and were implemented in the MADEX code to predict the spectrum. Fulvenallene has C 2v symmetry, hence we have included the statistical weights for 2 https://nanocosmos.iff.csic.es/ 3 http://www.iram.fr/IRAMFR/GILDAS

Fig. 2.
Observed lines with K a =0,1 of fulvenallene(c-C 5 H 4 CCH 2 ) towards TMC-1 (see line parameters in Table C.1). The abscissa corresponds to the rest frequency assuming a local standard of rest velocity of 5.83 km s −1 . The ordinate is the antenna temperature corrected for atmospheric and telescope losses in mK. The red line shows the synthetic spectrum derived for T rot =10 K and N(c-C 5 H 4 CCH 2 )=2.7×10 12 cm −2 . Blank channels correspond to negative features produced in the folding of the frequency switching data. Some K a =2,3 lines also appear in these panels (top left and fourth from bottom right). Additional K a =2,3 lines are shown in Fig. 3. the ortho and para species, 9 for ortho (K a odd) and 7 for para (K a even). The energy difference between the two states is 0.47 K.
We first searched for the strongest lines, which correspond to transitions with K a =0 and 1. All K a =0,1 lines within the Q band corresponding to transitions with J between 9 and 14 (a total of sixteen lines) are detected. These lines were found within 10-20 kHz of the predicted frequencies and are shown in Fig.  2. Their line parameters are given in Table C.1. Once the K a =0 and 1 lines were detected we searched for the less intense K a =2 and 3 transitions. Fourteen of these lines were detected and are  Figure 1, but for lines K a =2 and 3 (see line parameters in Table C.1).
shown in Fig. 3; their line parameters are given in Table C.1. We note that two of these lines are shown in Fig. 2 in the upper left panel and the fourth panel from the bottom on the right. Although the differences between the observed and predicted frequencies are small, they show a systematic behaviour; in particular, some of the K a =2,3 lines show discrepancies with respect to their frequencies as large as 50 kHz. Taking into account that the predictions in the Q band are strongly dependent on the low accuracy data of Sakaizumi et al. (1993) we fitted the frequencies of the TMC-1 lines alone to a Watson Hamiltonian in reduction A representation I r (Watson , 1977) using the FITWAT code (Cernicharo et al., 2018). This code reproduces the same results as the standard SPFIT code of Pickett (1991), as detailed in Appendix A of Cernicharo et al. (2018). The frequency measurements have been weighted as 1/σ 2 , where σ is the estimated frequency uncertainty. The resulting parameters are given in the first column of Table 1. The comparison with the fit to the laboratory data (middle column of the same Table) indicates that all the observed lines can be reproduced with rotational and distortion constants identical to those of the laboratory within the derived uncertainties of the different constants. Hence, the detection of fulvenallene is solid as it is based on 30 individual lines. Finally, taking into account that the accuracy of our measurements in the 31-50 GHz domain is better than those of Sakaizumi et al. (1993), we performed a merged fit to the laboratory and space frequencies of fulvenallene. The resulting constants are given in the third column of Table 1 and represent a significant improvement with respect to the constants obtained from the laboratory data alone (middle column of Table 1). The constants resulting from this merged fit are the ones we recommend to predict the spectrum of fulvenallene. The observed and calculated frequencies of the lines included in the fit, and the difference between the observed and calculated frequencies are given in Table C.2. Notes. Once we are confident of the detection of fulvenallene in TMC-1, we fitted the observed lines using a line profile fit method (Cernicharo et al., 2021e), which permits the rotational temperature and the column density to be fit, assuming that all levels have the same rotational temperature. A value of the dipole moment µ a =0.69±0.10 D was used (Sakaizumi et al. , 1993). We obtained a rotational temperature of 9±1 K and a column density of (2.7±0.3)×10 12 cm −2 . A rotational temperature lower than 8 K cannot reproduce the observed intensities of the K a =2,3 lines.
We also searched for fulvene (c-C 5 H 4 CH 2 ), for which the rotational spectroscopy has been accurately recorded by Mc-Carthy et al. (2020). The dipole moment of this molecule is µ a =0.424±0.001 D ( Baron et al., 1972), and hence for a column density similar to that of fulvenallene the lines will be 2.6 times weaker. Although some K a =0,1 lines are detected at a 3σ level we conclude that the molecule is below the present sensitivity limit of QUIJOTE. We obtain a 3σ upper limit to the column density of 3.5×10 12 cm −2 for fulvene.
Two derivatives of benzene are also of interest in the context of this work, toluene (c-C 6 H 5 CH 3 ) and styrene (c-C 6 H 5 C 2 H 3 ). For toluene, we used the laboratory data of Kisiel et al. (2004) and the dipole moment obtained by Rudolph et al. (1967), µ a =0.38±0.01 D. For styrene, laboratory spectroscopy up to 18 GHz is available from Caminati et al. (1988), who also derived the a and b components of the dipole moment as µ a =0.122±0.001 D and µ b <0.02 D. Due to the low dipole moment of the two species we derived relatively high 3σ upper limits, 6×10 12 cm −2 for toluene and 10 14 cm −2 for styrene. For both species we adopted a rotational temperature of 9 K.

Discussion
In the frame of a gas-phase bottom-up scenario for the formation of cycles in TMC-1, we ran chemical model calculations similar to those presented in Cernicharo et al. (2021f). Here we focus on cyclopentadiene and derivatives. Cyclopentadiene can be formed by two successive reactions involving the radical CH  Table A.1).
for which we adopted rate coefficients at 10 K of 3.3 × 10 −10 cm 3 s −1 (Loison et al., 2017) and 4 × 10 −10 cm 3 s −1 (Cernicharo et al., 2021f), respectively. In turn, the reaction of c-C 5 H 6 with CCH can yield various isomers of ethynyl cyclopentadiene, as well as fulvenallene We assumed a rate coefficient of 4 × 10 −10 cm 3 s −1 for reaction (3) and branching ratios of 0.25, 0.25, and 0.50 for channels (a), (b), and (c), respectively, where a higher branching ratio is adopted for fulvenallene because it is more stable than the isomers of ethynyl cyclopentadiene. The synthesis of c-C 5 H 6 therefore relies on 1,3-butadiene (CH 2 CHCHCH 2 ; non-polar and thus invisible at radio wavelengths), which in turn is formed from propene (CH 2 CHCH 3 ), whose abundance is well constrained in TMC-1 (Marcelino et al. , 2007). In the chemical model presented in Cernicharo et al. (2021f) this pathway produced cyclopentadiene with an abundance in agreement with observations because propene was formed very efficiently due to two consecutive radiative associations of CH 2 CCH + with H 2 (Herbst et al. , 2010), followed by dissociative recombination of C 3 H + 7 . This pathway is included in the chemical networks UMIST RATE12 (McElroy et al., 2013) and kida.uva.2014kida.uva. (Wakelam et al., 2015 and yields a very high propene abundance (see e.g. Agúndez & Wakelam 2013). However, the radiative associations mentioned above were later on shown to be inefficient at low temperatures (Lin et al., 2013). If they are neglected, the calculated abundance of propene drops by many orders of magnitude, well below the observed value, with drastic implications for the chemistry of many other hydrocarbons, such as 1,3-butadiene and cyclopentadiene, which are direct descendants of propene.
Currently, no efficient gas-phase route to propene has been identified in cold dark clouds. However, we know from observations that propene is present with a fairly large abundance.
To overcome the lack of formation of propene in our gas-phase chemical model, we fixed the peak abundance of propene to be in agreement with the value observed in TMC-1. The results from the chemical model are shown as solid lines in Fig. 4. It is seen that 1,3-butadiene is formed with an abundance ten times lower than propene, while c-C 5 H 6 in turn reaches an abundance ten times below that of 1,3-butadiene. However, according to the observations, the abundance of c-C 5 H 6 is only slightly below that of propene. The chemical model thus underestimates the abundance of c-C 5 H 6 by two orders of magnitude, and this translates directly to the derivatives of cyclopentadiene resulting from its reaction with CCH. In the case of 1-c-C 5 H 5 CCH, its calculated abundance is higher than that of 2-c-C 5 H 5 CCH and fuvenallene because it is formed through reaction (3), and in addition by the reaction between C 3 H and 1,3-butadiene (see Cernicharo et al. 2021e).
The fact that 1,3-butadiene and cyclopentadiene are firstand second-generation descendants of propene means that they reach progressively lower abundances. The resulting abundances are essentially controlled by the rates of formation, through reactions (1) and (2), and the rates of destruction, which in the chemical model is dominated by reaction with atomic carbon. We assumed rate coefficients of 10 −10 cm 3 s −1 for the reactions of atomic carbon with 1,3-butadiene and cyclopentadiene, in line with the values determined experimentally at low temperature for reactions between C and unsaturated hydrocarbons (Chastaing et al., 2001). In summary, regardless of what the true pathway to propene is, the consecutive reactions with CH are found to be insufficient to form cyclopentadiene with the observed abundance.
We examined possible formation routes to c-C 5 H 6 involving cations. Among them, the reaction between l-C 3 H + 3 and C 2 H 4 has been measured to be rapid, with a rate coefficient of 1.1 × 10 −9 cm 3 s −1 , and the ion C 5 H + 7 has been observed as product (Smyth et al., 1982;Anicich, 2003). Including this reaction in the chemical model and assuming that the ion C 5 H + 7 is cyclic and recombines dissociatively with electrons to yield c-C 5 H 6 with a standard rate coefficient of 10 −7 (T /300) −0.5 cm 3 s −1 , the calculated peak abundances of cyclopentadiene, and those of its CCH derivatives c-C 5 H 5 CCH and c-C 5 H 4 CCH 2 , become close to the observed values (see dashed lines in Fig. 4). Although our assumptions on the l-C 3 H + 3 + C 2 H 4 reaction require further exper-imental or theoretical support, this suggests that ion-neutral reactions can provide efficient formation routes to cycles in TMC-1. We note that c-C 3 H 3 + does not react with C 2 H 4 (Smyth et al., 1982;Anicich, 2003).
To have some insight into the possible precursors of hydrocarbon cycles we collected abundances for hydrocarbons C n H m detected in TMC-1. The abundances derived from QUIJOTE data from previous publications of our team related to newly detected hydrocarbons, and for species already known but with transitions in our frequency range, are given in Table A.1 and represented in Fig. 5. For species such as benzene or naphthalene we adopted an abundance ratio between them and their cyano derivatives of 5-10. We note however that these estimates are very uncertain. From Fig. 5 it appears that the most abundant hydrocarbon radicals are methylidyne (CH), ethynyl (CCH), propargyl (CH 2 CCH), and butadiynyl (C 4 H). The most abundant closed shell hydrocarbons are methylacetylene (CH 3 CCH), cyclopropenylidyne (c-C 3 H 2 ), ethylene (C 2 H 4 ), and propene (CH 2 CHCH 3 ). Indene is the most abundant cycle with more than three carbon atoms, followed by cyclopentadiene, benzene, naphthalene, and benzyne. If these rings are formed in the gas phase, their precursors should be among the abundant species with 3-5 carbon atoms. The role of hydrocarbon cations (C n H m + ) in the chemistry of hydrocarbons has been quite well studied, but their abundances remain unknown. Only C 3 H + and C 5 H + have been detected in TMC-1 so far (Cernicharo et al., 2022). Moreover, the abundance of important species for hydrocarbon chemistry, such as CH 3 , CH 4 , C 2 H 2 , CH 2 CH 2 , CH 3 CH 3 , and CH 3 CH 2 CH 3 , remain unknown because they are non-polar, and thus cannot be observed at radio wavelengths. For CH 2 CH 2 we used the derived abundance of vinyl acetylene (see Appendix A) since molecular beam experiments and electronic structure calculations provide compelling evidence that it is formed in the reaction of ethylene and the ethynyl radical (Zhang et al. , 2009). Similarly, for CH 3 CH 3 we can estimate its abundance from that of CH 3 CH 2 CCH (Cernicharo et al., 2021d). These estimates are, as for benzene and naphthalene, very uncertain (see Appendix A).

Conclusions
We detected fulvenallene in TMC-1, with an abundance just 4.4 times lower than its possible precursor cyclopentadiene and similar to those of the two ethynyl cyclopentadiene isomers detected in this source. Fulvenallene and ethynyl cyclopentadiene are most likely formed by the reaction between cyclopentadiene and CCH. However, our chemical model, mainly based on neutral-neutral gas-phase reactions, undererstimates the abundance of cyclopentadiene by two orders of magnitude. We suggest that ion-neutral gas-phase reactions between the most abundant cations and hydrocarbons, open and closed shell species, may provide efficient routes to cyclopentadiene and other cycles in TMC-1.  Table A.1 in Appendix A. The abscissa corresponds to the number of carbon atoms in the molecule and the ordinate to the column density of each hydrocarbon. For species whose abundance has been estimated from cyano derivatives the upper and lower ranges are indicated by two green squares. For the other species the abundance is indicated by a single red square and the error is represented by a vertical black line. Abundances of the most abundant cations, according to the chemical model (see text), are indicated in magenta.
A&A proofs: manuscript no. 44399 Rudolph, H.D., Jaeschke, A. & Wendling, P. 1967, Z. Naturforschg 22a, 940 Sakai, N., Saruwatari, O., Sakai, T., et al. 2010, A&A, 512, A31 Sakaizumi, T., Katoh, F., Ohashi, O. & Yamaguchi, I. 1993, J. Mol. Spectrosc., 159, 112 Smyth, K. C., Lias, S. G., & Ausloos, P. 1982, Combust. Sci. Technol., 28, 147 Tercero, F., López-Pérez, J. A., Gallego, et al. 2021, A&A, 645, A37 Wakelam, V., Loison, J.-C., Herbst, E., et al. 2015, ApJS, 217, 20 Watson, J.K.G 1977, 6, 1 Zhang, F., Kim, S., Kaiser, R.I. et al. 2009, J. Phys. Chem. A, 113, 11167 Appendix A: Abundance of the C n H m hydrocarbons in TMC-1 In order to have a global view of the abundances of hydrocarbons in TMC-1, we show in Table A.1 the values obtained with QUIJOTE for most species of interest related to this work. In all cases we assumed a source diameter of 80 (Fossé et al., 2001). Some of the species given in this table have rotational transitions within the QUIJOTE survey, but their data have not been published yet. Most of them have been previously detected by other authors. Nevertheless, we think it more valuable to provide column densities using the QUIJOTE data to have a coherent criteria in the determination of their column densities, and to use data gathered with the same radio telescope. The data on these species will be published elsewhere. Here we comment briefly on the assumptions adopted for these molecules to derive the column densities given in Table A.1. In all cases, except when indicated, the adopted line width at half intensity, ∆v, is 0.6 km s −1 .
For l-C 3 H, only one rotational transition, J=3/2-1/2, with six fine and hyperfine components is covered within the QUIJOTE frequency range. All these lines are detected with very high S/N values. We adopted T rot =7 K for linear C 3 H. The derived column density is (6.0±0.6)×10 12 cm −2 . We note that the column density is not very sensitive to the adopted rotational temperature for T rot between 6 and 10 K. This is due to the low energy (E u =1.57 K) of the upper level J=3/2 (see Appendix A of Cernicharo et al. 2021g).
Only the rotational transition 2 11 -2 12 of c-C 3 H falls within the QUIJOTE survey. It exhibits several fine and hyperfine components. The energy or the upper level of 6.52 K, hence slightly more sensitive to the adopted rotational temperature than C 3 H. The derived column density is (1.2±0.3)×10 12 cm −2 for T rot =5 K and (9.0±0.9)×10 11 cm −2 for T rot =7 K.
For the hydrocarbon anions C 4 H − , C 6 H − , and C 8 H − , and for their neutral counterparts C 4 H, C 6 H, and C 8 H, column densities were derived from all data available in the literature plus the QUIJOTE data. For these species, we derived column densities using both the LVG method and the rotation diagram method. In Table A.1 we give values of their column densities, where the uncertainty corresponds to the values derived from these two methods. More details will be given in a separate publication (Agúndez et al., in preparation).
Several transitions of C 7 H are present within the survey. Their intensities are well reproduced with T rot =7 K and a column density of (6.5±0.6)×10 10 cm −2 . For C 9 H we derived only a 3σ upper limit of 3.5×10 10 cm −2 adopting a rotational temperature of 10 K.
Several hydrocarbons of interest for this work have a zero dipole moment, and hence their abundances were estimated from their CCH or CN derivatives. We assumed an abundance ratio between the mother molecule and its cyano derivatives (benzene and naphthalene) of 5-10. In the case of ethynyl derivatives (C 2 H 4 , C 2 H 6 ) the adopted abundance ratio is 3-6; however, these estimates are very uncertain.

Appendix B: Data analysis
The raw data of the QUIJOTE survey was processed always following the same procedure for each observing run, which typically consist of 100-120 hours of observing time on the source. Each FFT spectrometer was divided into 160 subsections of 400 channels. Ripples with frequencies ≤5 MHz can be easily removed with the FFT command of the CLASS program of the GILDAS package. For each sub-band of 400 channels, a comparison of the sum of the raw data (averaged weighting by system temperature and integration time), the data with ripples was removed, and the results of the previous runs was performed to define line windows around features with intensity above 4σ, and also to remove instrumental spurious features, atmospheric lines, and well-known features arising in the down-conversion chain. Once this process was achieved, then all raw scans of a given run were processed removing a polynomial baseline. Taking into account that the lines have a width of 2-3 channels at half intensity, this baseline removal does not affect the line profiles. Once the baselines for all the scans of each 400-channel sub-band were removed, the data were averaged, but this time with weights proportional to 1/σ 2 . Because each run consists typically of 1000-2000 individual scans this procedure gives little statistical weight to scans that have a greater noise value than expected without having to explore all the individual scans. This rather tedious procedure yields flat baselines and full confidence in the spectral purity. A total of 2560 blocks of 400 channels have been analysed for each observing run (160× 8 spectrometers × two polarisations). Except for the first run for which the information used on the lines appearing in TMC-1 was that provided by the Nobeyama line survey of TMC-1 (Kaifu et al., 2004), for all the other runs QUIJOTE itself was the source of information on the spectral features present in each 400-channel sub-band. The final spectrum contains 507017 channels with a width of 38.15 kHz.