THE OBSERVATION AND PROPERTIES OF (H2O⋯HCl)⋯Ar(H_{2}O\cdots HCl)\cdots Ar

$^{a}$Z. Kisiel, B. A. Pietrewicz, P. W. Fowler, A. C. Legon, E. Steiner, J. Phys. Chem. A 104, 6970 (2000) $^{b}$Z. Kisiel, E. Bialkowska-Jaworska, L. Pszcz\'{o}lkowski, A. Milet, C. Struniewicz, R. Moszynski, J. Sadlej, J. Chem. Phys. 112, 5767 (2000) $^{c}$Z. Kisiel, J. Mol. Spectrosc. 218, 58 (2003)Author Institution: Institute of Physics, Polish Academy of SciencesThe trimer $(H_{2}O\cdots HCl)\cdots Ar$ was observed in this laboratory by supersonic expansion cavity-FTMW spectroscopy, during the work carried out on $H_{2}O\ldots HCl^{a}$ and $(H_{2}O)_{2}HCl.^{b}$ The title trimer appears to be useful test-bed for detailed assessment of the effect of complexing a Rare-gas atom to the more strongly bound $H_{2}O\cdots HCl$ subunit. $(H_{2}O\cdots HCl)\cdots Ar$ is near-planar and since the $H_{2}O\cdots HCl$ unit is oriented at $\approx 27^{\circ}$ to the b-inertial axis both the $\mu_{b}$ and the $\mu_{a}$ dipole moment components are appreciable, giving rise to a rich rotational spectrum. Presently we present a summary of the information obtained for this trimer. Five different isotopomers of the trimer, resulting from $^{37}Cl, D$, and $^{18}O$ substitution, have been observed. In addition to the usual spectroscopic constants it was possible to determine accurate values of the $\chi_{ab}$ nuclear quadrupolar splitting constant for the chlorine nucleus, and thus the principal nuclear quadrupole tensor and the associated rotation angle. Electric dipole moment of the trimer was measured and supporting ab initio calculations at the MP2/aug-cc-pVTZ level were carried out. Following a recent test of the applicability of the $r_{m}$ method to weakly bound $complexes^{c}$ we derived such a geometry for $(H_{2}O\cdots HCl)\cdots Ar$ and find it to be in satisfactory agreement with the ab inito calculations. Comparison of results obtained for the trimer with the accurate data available for $H_{2}O\cdots HCl$ allow the effects of this first step in inert-gas matrix isolation of $H_{2}O\cdots HCl$ to be identified

THE ROTATIONAL SPECTRUM OF CHLORINE NITRATE (ClONO2_2): ν6\nu_6 AND THE ν5\nu_5/ν6ν9\nu_6\nu_9 DYAD

Author Institution: Institute of Physics, Polish Academy of Sciences, Al. Lotnikow; 32/46, 02-668 Warszawa, Poland; Department of Physics, Pittsburg State University, Pittsburg, KS 66726; Department of Physics, Wright State University, Dayton, OH 45435; Department of Physics, University of South Alabama, Mobile, Al 36688; Department of Physics, The Ohio State University, Columbus,; OH 43210Chlorine nitrate is an important stratospheric molecule and analyses of extensive measurements of rotational transitions in the ground state and $\nu_9$ (120 cm$^{-1}$)}, 363-378 (1997).}, the 2$\nu_9$/$\nu_7$ dyad (262 cm$^{-1}$)}, 8-14 (2002).}, and the 3$\nu_9$/$\nu_7\nu_9$ dyad (361 cm$^{-1}$)}, 150-152 (2003).} have already been reported. The available experimental data for ClONO$_2$ have been extended by a new FASSST spectrum recorded between 118-378 GHz at greater sensitivity and resolution than hitherto and on a more pure sample. \vspace{0.2cm} The new spectrum allowed an improvement in the spectroscopic constants for the ground state and $\nu_9$, as well as more confident assignment of rotational transitions in higher vibrational states. Application of the AABS package for $Assignment and Analysis of Broadband Spectra$}}kisiel/prospe.htm} was crucial in keeping track of the transitions already assigned and rapid extension of datasets for new states. The analyses of the relatively isolated $\nu_6$ (435 cm$^{-1}$) and of the $\nu_5$/$\nu_6\nu_9$ dyad (551 cm$^{-1}$) have now been completed for both $^{35}$ClONO$_2$ and $^{37}$ClONO$_2$. In the parent isotopologue the $\nu_5$ and $\nu_6\nu_9$ states are found to be 4.124652(6) cm$^{-1}$ apart and to be connected by a sufficiently strong Coriolis interaction to give rise to measurable interstate transitions and to perturbed hyperfine splitting patterns

Millimetre-wave laboratory study of glycinamide and a search for it with ALMA towards Sagittarius B2(N)

International audienceGlycinamide (NHCHC(O)NH) is considered to be one of the possible precursors of the simplest amino acid, glycine. Its only rotational spectrum reported so far has been in the centimetre-wave region on a laser-ablation generated supersonic expansion sample. Aims. The aim of this work is to extend the laboratory spectrum of glycinamide to the millimetre (mm) wave region to support searches for this molecule in the interstellar medium and to perform the first check for its presence in the high-mass star forming region Sagittarius B2(N). Methods. Glycinamide was synthesised chemically and was studied with broadband rotational spectroscopy in the 90-329 GHz region with the sample in slow flow at 50°C. Tunnelling across a low-energy barrier between two symmetry equivalent configurations of the molecule resulted in splitting of each vibrational state and many perturbations in associated rotational energy levels, requiring careful coupled state fits for each vibrational doublet. We searched for emission of glycinamide in the imaging spectral line survey ReMoCA performed with the Atacama Large Millimetre/submillimetre Array towards Sgr B2(N). The astronomical spectra were analysed under the assumption of local thermodynamic equilibrium. Results. We report the first analysis of the mm-wave rotational spectrum of glycinamide, resulting in fitting - to experimental measurement accuracy - of over 1200 assigned and measured transition frequencies for the ground-state tunnelling doublet and of many lines for tunnelling doublets for two singly excited vibrational states. We also determine the precise vibrational separation in each doublet. We did not detect emission from glycinamide in the hot molecular core Sgr B2(N1S). We derived a column density upper limit of 1.5 × 1016 cm-2, which implies that glycinamide is at least seven times less abundant than aminoacetonitrile and 1.8 times less abundant than urea in this source. A comparison with results of astrochemical kinetics models for species related to glycinamide suggests that its abundance may be at least one order of magnitude below the upper limit obtained towards Sgr B2(N1S). This means that glycinamide emission in this source likely lies well below the spectral confusion limit in the frequency range covered by the ReMoCA survey. Conclusions. Thanks to the spectroscopic data provided by this study, the search for glycinamide in the interstellar medium can continue on a firm basis. Targetting sources with a lower level of spectral confusion, such as the Galactic Center shocked region G+0.693-0.027, may be a promising avenue. © ESO 2022