Open resource for spectroscopic raw data Is anyone aware of reliable resources (ideally public) which allow the user to download the raw spectroscopic data such as infrared spectrum of small organic molecules, or rotational spectrum of HCl/DCl mixtures or NMR spectra of molecules? I was looking at the NIST database but apparently there is no option for downloading the spectrum as an Excel, csv or txt file. Thanks.

NIST Spectral Database
As a quick fix: To access the IR spectral data of $\ce{HCl}$, I opted for a seach by (Hill) formula  on NIST's web page, which yielded three entries here.  For $\ce{HCl}$ in particular (here) I opted for the first one here, indeed offering the spectrum as image file or as JCAMP-DX.

As in the comment by @EdV, this JCAMP-DX an ASCII file indeed.  Note JDXview by Norbert Haider (Department of Drug Synthesis, University of Vienna, Austria) is a very handy program (only 560 kb, installation free executable) for a quick display of this file by NIST. Via File -> Save, the export of the data in a two-column, tabulator separated .txt file is just a click away.  The program works perfectly well in Windows, and with wine libraries equally in Linux, too.  (The author equally distributes the underlying Delphi / Pascal code.)



Note 1: Because of the tags physical chemistry, and spectroscopy, you may be interested in a python module like jcamp to access either IR, or NMR spectra in the JCAMP-DX formats (there are multiple).

Note 2: Sometimes, all you have indeed is an image (a scanned) spectrum.  If you pay attention and proceed in sections (e.g., $4000 - 2000$, then $2000 - 800\,\pu{cm^{-1}}$) to account for the break on the abscissa in IR spectroscopy, a digitizer like WebPlotDigtizer may be worth to use.  If you want, the program works via a web browser, installation free, with «normal image files» like .png, and since some time with images embedded in a .pdf (think about publications), too.