A Status Report On The Cologne Database For Molecular Spectroscopy, Cdms

The CDMS\footnote{Shortcut: cdms.de; web address: https://cdms.astro.uni-koeln.de/. The CDMS is supported by the Verbundforschung Physik of the BMBF (German Ministry of Science and Education), project ID 05A17PK1.} was founded more than 20 years ago to provide in its catalog section line lists of mostly molecular species which were or may be detected in space by radio astronomical means.\footnote{H.~S.~P. M\"uller et al., Astron. Astrophys. 370 (2001) L49.} The line lists are generated by fitting critically evaluated experimental data, mostly from laboratory spectroscopy, to established Hamiltonian models. The assessment of the experimental data and of the Hamiltonian model is very important\footnote{e.g., C.~P. Endres et al., J. Mol. Spectrosc. 327 (2016) 95.} and will be discussed in some detail. There are 1051 entries in the CDMS catalog as of end of Feb. 2021. A large fraction of the contribution will deal with recent entries and with potential laboratory needs which are often linked to Atacama Large Millimeter/submillimeter Array projects such as (R)EMoCA\footnote{(Re-) Exploring Molecular Complexity with ALMA, A. Belloche et al., Astron. Astrophys. 587 (2016) A91 \& 628 (2019) A10.}, PILS\footnote{The ALMA Protostellar Interferometric Line Survey, J.~K. J{\o}rgensen et al., Astron. Astrophys. 595 (2016) A117.}, and ATOMIUM.\footnote{ALMA Tracing the Origins of Molecules forming dust In oxygen-rich M-type stars, L. Decin et al., Science 369 (2020) 1497.} These include numerous diatomics, frequently containing metals, with highly excited states and isotopic species for several molecules already detected in space for the last project and excited states or isotopic species of known interstellar organic molecules, but also several new ones for the other projects. Other sections of the classical CDMS include a page on Molecules in Space and a help page for users of Pickett's SPFIT/SPCAT programs. There is also a VAMDC compatible incarnation of the CDMS which is linked to a plethora of other spectroscopic, collisional, and kinetic databases via the Vitual Atomic and Molecular Data Centre portal.\footnote{http://www.vamdc.org/

Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide

The largest non-cyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times that of its straight-chain structural isomer. This detection suggests that branched carbon-chain molecules may be generally abundant in the ISM. Our astrochemical model indicates that both isomers are produced within or upon dust grain ice mantles through the addition of molecular radicals, albeit via differing reaction pathways. The production of iso-propyl cyanide appears to require the addition of a functional group to a non-terminal carbon in the chain. Its detection therefore bodes well for the presence in the ISM of amino acids, for which such side-chain structure is a key characteristic.Comment: This is the author's version of the work. It is posted here by permission of the AAAS for non-commercial use. The definitive version was published in Science 345, 1584 (2014), doi:10.1126/science.125667

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

The discovery of amino acids in meteorites and the detection of glycine in samples returned from a comet to Earth suggest that the interstellar chemistry is capable of producing such complex organic molecules. Our goal is to investigate the degree of chemical complexity that can be reached in the ISM. We performed an unbiased, spectral line survey toward Sgr B2(N) and (M) with the IRAM 30m telescope in the 3mm window. The spectra were analyzed with a simple radiative transfer model that assumes LTE but takes optical depth effects into account. About 3675 and 945 spectral lines with a peak signal-to-noise ratio higher than 4 are detected toward N and M, i.e. about 102 and 26 lines per GHz, respectively. This represents an increase by about a factor of 2 over previous surveys of Sgr B2. About 70% and 47% of the lines detected toward N and M are identified and assigned to 56 and 46 distinct molecules as well as to 66 and 54 less abundant isotopologues of these molecules, respectively. We also report the detection of transitions from 59 and 24 catalog entries corresponding to vibrationally or torsionally excited states of some of these molecules, respectively. Excitation temperatures and column densities were derived for each species but should be used with caution. Among the detected molecules, aminoacetonitrile, n-propyl cyanide, and ethyl formate were reported for the first time in space based on this survey, as were 5 rare isotopologues of vinyl cyanide, cyanoacetylene, and hydrogen cyanide. We also report the detection of transitions from within 12 new vib. or tors. excited states of known molecules. Although the large number of unidentified lines may still allow future identification of new molecules, we expect most of these lines to belong to vib. or tors. excited states or to rare isotopologues of known molecules for which spectroscopic predictions are currently missing. (abridged)Comment: Accepted for publication in A&A. 266 pages (39 pages of text), 111 tables, 8 figure

The CDMS view on molecular data needs of Herschel, SOFIA, and ALMA

The catalog section of the Cologne Database for Molecular Spectroscopy, CDMS, contains mostly rotational transition frequencies, with auxiliary information, of molecules observable in space. The frequency lists are generated mostly from critically evaluated laboratory data employing established Hamiltonian models. The CDMS has been online publicly for more than 12 years, e.g., via the short-cut http://www.cdms.de. Initially constructed as ascii tables, its inclusion into a database environment within the Virtual Atomic and Molecular Data Centre (VAMDC, http://www.vamdc.eu) has begun in June 2008. A test version of the new CDMS is about to be released. The CDMS activities have been part of the extensive laboratory spectroscopic investigations in Cologne. Moreover, these activities have also benefit from collaborations with other laboratory spectroscopy groups as well as with astronomers. We will provide some basic information on the CDMS and its participation in the VAMDC project. In addition, some recent detections of molecules as well as spectroscopic studies will be discussed to evaluate the spectroscopic data needs of Herschel, SOFIA, and ALMA in particular in terms of light hydrides, complex molecules, and metal containing speciesComment: 14 pages, 1 figure; AIP Conf. Proc., accepted; Proceedings of the Eighths International Conference on Atomic and Molecular Data and Their Applicatio

Exploring molecular complexity with alma (EMoCA): high-angular-resolution observations of sagittarius B2(N) at 3 mm

Sagittarius (Sgr for short) B2 is the most massive and luminous star-forming region in our Galaxy, located close to the Galactic Center. We have carried out a molecular line survey with the IRAM~30~m telescope toward its two major sites of star-formation, Sgr~B2(M) and (N).footnote{A. Belloche et al., textit{A&A} textbf{559} (2013) Art. No. A47.} Toward the latter source, which is particularly rich in Complex Organic Molecules (COMs), we detected three molecules for the first time in space, aminoacetonitrile, ethyl formate, and textit{n}-propyl cyanide. We have recently obtained ALMA data of Sgr~B2(N) between $sim$84 and $sim$111~GHz within Cycle~0 and one additional setup up to 114.4~GHz within Cycle~1. At angular resolutions of $1.8''$ and $1.4''$, respectively, the two main hot cores, the prolific Sgr~B2(N-LMH) (or Sgr~B2(N)-SMA1) and the likely less evolved Sgr~B2(N)-SMA2 are well separated, and line confusion is reduced greatly for the latter. As a consequence, we have been able to identify the first branched alkyl molecule in space, textit{iso}-propyl cyanide, toward Sgr~B2(N)-SMA2.footnote{A. Belloche et al., textit{Science} textbf{345} (2014) 1584.} Our ongoing analyses include investigations of cyanides and isocyanides, alkanols and thioalkanols, and deuterated molecules among others. We will present some of our results

A STATUS REPORT ON THE COLOGNE DATABASE FOR MOLECULAR SPECTROSCOPY, CDMS

The CDMS\footnote{Shortcut: cdms.de; web address: https://cdms.astro.uni-koeln.de/. The CDMS is supported by the Verbundforschung Physik of the BMBF (German Ministry of Science and Education), project ID 05A17PK1.} was founded more than 20 years ago to provide in its catalog section line lists of mostly molecular species which were or may be detected in space by radio astronomical means.\footnote{H.~S.~P. M\"uller et al., Astron. Astrophys. 370 (2001) L49.} The line lists are generated by fitting critically evaluated experimental data, mostly from laboratory spectroscopy, to established Hamiltonian models. The assessment of the experimental data and of the Hamiltonian model is very important\footnote{e.g., C.~P. Endres et al., J. Mol. Spectrosc. 327 (2016) 95.} and will be discussed in some detail. There are 998 entries in the CDMS catalog as of Feb. 01 2020. A large fraction of the contribution will deal with recent entries and with potential laboratory needs which are often linked to Atacama Large Millimeter/submillimeter Array projects such as (R)EMoCA\footnote{(Re-) Exploring Molecular Complexity with ALMA, A. Belloche et al., Astron. Astrophys. 587 (2016) A91 \& 628 (2019) A10.}, PILS\footnote{The ALMA Protostellar Interferometric Line Survey, J.~K. J{\o}rgensen et al., Astron. Astrophys. 595 (2016) A117.}, and ATOMIUM.\footnote{ALMA Tracing the Origins of Molecules forming dust In oxygen-rich M-type stars, L. Decin et al. (2020) submitted.} These include numerous diatomics, frequently containing metals, with highly excited states and isotopic species for several molecules already detected in space for the last project and excited states or isotopic species of known interstellar organic molecules, but also several new ones for the other projects. Other sections of the classical CDMS include a page on Molecules in Space and a help page for users of Pickett's SPFIT/SPCAT programs. There is also a VAMDC compatible incarnation of the CDMS which is linked to a plethora of other spectroscopic, collisional, and kinetic databases via the Vitual Atomic and Molecular Data Centre portal.\footnote{http://www.vamdc.org/

THE ROTATIONAL SPECTRUM OF THE METHANETHIOL ISOTOPOLOG CH334SH

Methanethiol, CH$_3$SH, has been found in the warm and dense parts of high as well as low mass star-forming regions.\footnote{See, e.g., H. S. P. M{\"u}ller at al., Astron. Astrophys. 587 (2016) A92; M. N. Drozdovskaya et al., Mon. Not. R. Astron. Soc., accepted, arXiv: 1802.02977; and references therein.} The molecule is also of fundamental interest because of the large amplitude internal rotation of the CH$_3$ group whose effects are somewhat less pronounced than in its lighter homolog CH$_3$OH. In the course of our ongoing study of CH$_3^{32}$SH,\footnote{V. Ilyushin et al., TI04 at the 72nd ISMS, 2017} we have recorded new spectra which currently cover 49$-$510~GHz.\footnote{The work in Kharkov was done under support of the Volkswagen foundation. The assistance of the Science and Technology Center in the Ukraine is acknowledged (STCU partner project \#P686). The work in Cologne was supported by the Deutsche Forschungsgemeinschaft (DFG) via grant SFB~956, project B3 and via the Ger{\"a}tezentrum ''Cologne Center for Terahertz Spectroscopy''.} These spectra, as well as existing ones covering part of the 1.1$-$1.5~THz region,\footnote{L.-H. Xu at al., J. Chem. Phys. 137 (2012) 104313.} were inspected for lines of CH$_3^{34}$SH. We made extensive assignments of $\Delta K = 0$ transitions in $v_t = 0$ to 2. Numerous assignments of $\Delta K = \pm1$ transitions were made in $v_t = 0$ and to a lesser extent in the two higher torsional states. We will present results of modeling these data with the RAM36 program and of searches for this isotopolog in our 3~mm ALMA data of Sagittarius~B2(N)

ROTATIONAL SPECTROSCOPY OF THE LOW ENERGY CONFORMER OF 2-METHYLBUTYRONITRILE AND SEARCH FOR IT TOWARD SAGITTARIUS B2(N2)

Quite recently, some of us detected \textit{iso}-propyl cyanide as the first branched alkyl molecule in space.\footnote{A. Belloche, R.~T. Garrod, H.~S.~P. M{\"u}ller, and K.~M. Menten, \textit{Science} \textbf{345} 1584.} The identification was made in an ALMA Cycle~0 and 1 molecular line survey of Sagittarius~B2(N) at 3~mm. The branched isomer was only slightly less abundant than its straight-chain isomer with a ratio of about 2\,:\,5. While initial chemical models favored the branched isomer somewhat, more recent models\footnote{R.~T. Garrod, A. Belloche, H.~S.~P. M{\"u}ller, and K.~M. Menten, \textit{Astron. Astrophys.}, in press; doi: 10.1051/0004-6361/201630254.} are able to reproduce the observed ratio. Moreover, the models predicted that among the next longer butyl cyanides (BuCNs) 2-methylbutyronitrile (2-MBN) should be more abundant than both $n$-BuCN and 3-MBN by factors of around 2, with $t$-BuCN being almost negligible._x000d_ _x000d_ With the rotational spectra of $t$- and $n$-BuCN studied,\footnote{Z. Kisiel, \textit{Chem. Phys. Lett.} \textbf{118} 134; M.~H. Ordu et al., \textit{Astron. Astrophys.} \textbf{541} A121.} we investigated those of 2-MBN and 3-MBN betwen $\sim$40 and $\sim$400~GHz by conventional absorption spectroscopy and by chirped-pulse and resonator Fourier transform microwave (FTMW) spectroscopy. The analyses were guided by quantum-chemical calculations._x000d_ _x000d_ Here we report the analysis of the low-energy conformer of 2-MBN and a search for it in our current ALMA data. Two additional conformers are higher by $\sim$250 and $\sim$280~cm$^{-1}$. The low-energy conformer displays a very rich rotational spectrum because of its great asymmetry ($\kappa \approx 0.14$) and large $a$- and $b$-dipole moment components. Accurate $^{14}$N quadrupole coupling parameters were obtained from the FTMW spectral recordings