We report the observation and assignment of the rotational spectra of the isotopically chiral molecule, trans-2,3-dideutero-oxirane (c-CHD-CHDO) measured in the gigahertz range of 62-110 GHz and in the terahertz range, 25-80 cm⁻¹(instrumental resolution of 0.00052 cm⁻¹). Normal oxirane (c-C₂H₄O) has been detected by astrophysical spectroscopy in space.J. E. Dickens, et al., ApJ, 1997, 489, 753; M. Ikeda, et al., ApJ, 2001, 560, 792; J. M. Lykke, et al., A&A,2017, 597, A53.A small number of lines of trans−2,3−dideutero−oxirane had been previously analyzed in the microwave regionC. Hirose, Bull. Chem. Soc. Jap., 1974, 47, 1311. up to 70 GHz. We have recently S. Albert, Z. Chen, K. Keppler, Ph. Lerch, M. Quack, V. Schurig, O. Trapp, Phys.Chem.Chem.Phys., 2019, 21, 3669 measured and successfully analyzed the rotational spectrum of monodeutero−oxirane between 65 and 119 GHz using our GHz spectrometer,M. Suter, M. Quack, Appl. Opt., 2015, 54 (14), 4417; S. Albert, Z. Chen, C. Fabri, Ph. Lerch, R. Prentner, M. Quack, Mol. Phys., 2016, 114, 2751. and in the 0.75 to 2.5 THz range measured with our FTIR setup S. Albert, Ph. Lerch, M. Quack, ChemPhysChem, 2013, 14, 3204; S. Albert, K. K. Albert, Ph. Lerch, M. Quack, Faraday Discuss., 2011, 150, 71. at the Swiss Light Source.In the current work, we were able to assign and analyze more than 2500 rotational transitions of the vibronic ground state of trans−2,3−dideutero−oxirane up to J=65. The molecule is also of interest in the context of molecular parity violation, similar to the related molecules.M. Quack and G. Seyfang, Tunnelling and parity violation in chiral and achiral molecules, ch.6 in Tunnelling in Molecules, J.Kaestner and S. Kozuch eds.,pp 192-244, RSC publishing, Cambridge 2020, and references cited therein. Our results are important in relation to isotopic chirality and parity violation, C. Hirose, Bull. Chem. Soc. Jap., 1974, 47, 1311.M. Suter, M. Quack, Appl. Opt., 2015, 54 (14), 4417; S. Albert, Z. Chen, C. Fabri, Ph. Lerch, R. Prentner, M. Quack, Mol. Phys., 2016, 114, 2751.M. Quack and G. Seyfang, Tunnelling and parity violation in chiral and achiral molecules, ch.6 in Tunnelling in Molecules, J.Kaestner and S. Kozuch eds.,pp 192-244, RSC publishing, Cambridge 2020, and references cited therein.

Ever-increasingly complex molecules are being searched for in the interstellar medium, and following the detections of propylene oxide McGuire, B. A., Carroll, P. B., Loomis, R. A., et al. 2016, Science, 352, 1449nd benzonitrile McGuire, B. A., Burkhardt, A. M., Kalenskii, S., et al. 2018, Science, 359, 202 chiral and aromatic molecules are becoming appealing targets for laboratory studies and interstellar searches. The chiral molecule styrene oxide (C₆H₅C₂H₃O), also known as phenyloxirane, is an epoxide (R−C₂H₃O) with a phenyl ring as the (-R) substituent. With a single conformer and a permanent dipole moment of about 1.8 Debye, styrene oxide emerges as an interesting chiral molecule for astrochemical investigations. We investigated the microwave and millimeter wave spectrum of styrene oxide and analysed the ground-state rotational spectrum as well as rotational transitions from low-energy vibrationally excited states. Chirped-pulse Fourier-transform microwave and millimeter-wave spectroscopy and frequency modulation absorption spectroscopy were used to record spectra in the regions of 2-12 GHz, 75-110 GHz, 170-220 GHz, and 260-330 GHz. From the spectral analysis, a set of precise rotational and centrifugal distortion parameters up to the sextic order was obtained. Our accurate predictions of styrene oxide into the (sub-)millimeter range are mandatory for radio astronomy searches with state-of-the-art observational facilities, such as ALMA. In addition, we assigned the spectra of all singly-substituted ¹³C and ¹⁸O isotopologues, which allowed us to determine the gas phase structure of the molecule experimentally. McGuire, B. A., Carroll, P. B., Loomis, R. A., et al. 2016, Science, 352, 1449a McGuire, B. A., Burkhardt, A. M., Kalenskii, S., et al. 2018, Science, 359, 202,

The hydroxymethyl (CH₂OH) and methoxy (CH₃O) radicals, products of CH₃OH photodissociation, are considered key reactive intermediates in the interstellar medium (ISM), and their recombination with other fragments is postulated to lead to the formation of commonly observed complex organic molecules (COMs) as glycolaldehyde, ethanol, ethylene glycol, and dimethyl ether. Interestingly, despite the recent first laboratory detection of CH₂OH pure rotational spectrum [1] and while this isomer is the most thermodynamically stable, only CH₃O has so far been detected in the ISM. A plausible explanation to this lack of interstellar detection is the non-observation in the laboratory of the most intense transitions at low temperature. We have re-investigated the pure rotational spectrum of CH₂OH at room temperature in the millimeter-wave domain, using a frequency modulation submillimeter spectrometer, with emphasized searches for the fundamental b-type transitions and those intense at low temperature. The radical was produced by H abstraction from CH₃OH using F atoms produced by a microwave discharge. A combined fit of millimeter-wave lines from the literature and our new measurements using a rigid-rotor Hamiltonian yielded a large improvement in the spectroscopic parameters [2] values allowing now confident searches of CH₂OH in cold interstellar environments. [1] C. Bermudez et al., Astronomy and Astrophysics (2017) 598, A 9 [2] O. Chitarra et al., Astronomy and Astrophysics (2020) 644, A 123

The knowledge of synthetic routes of complex organic molecules is still far to be fully understood. The creation of reliable models is particularly challenging. Hollis et al.Hollis, J. M.; et al., 2006, ApJ 642, 933ointed out that the observations of molecular isomers provides an excellent tool to evaluate the hypothesis of the synthetic pathways. Formamide (HC(O)NH₂) is an abundant molecule in ISM detected in 1971 in SgrB2Rubin, R. H. ; et al., 1971, ApJ 169, L39 Since formaldoxime and nitrosomethane are two isomers of formamide, they are interesting ISM targets. Up to now the spectroscopic studies are only available up to 40 GHzKaushik V. K. ; et al., 1978, J. Phys. Soc. Jap. 45, 1975Turner P. H. et al., 1978, J. Chem. Soc., Faraday Trans. 2 74, 533. We reinvestigated the spectra of both isomers in the submillimeterwave domain in order to provide more accurate prediction to permit their possible detection in ISM. These two molecules are not commercially available and shoud be synthesized. The spectra were recorded in Lille from 150 to 660 GHz. In the region below 500 GHz we used the new Fourier transform millimeter-wave (FTmmW) spectrometer system based on DDS particulary suitable for unstable speciesZou L.; et al., 2019, 74^th ISMS, Champaign USA FB04 Both analysis are not obvious, formaldoxime has a small dipole moment value: 0.2 Debye, giving weak transitions in the observed spectra. Concerning nitrosomethane, the methyl top internal rotation should be taken into account, therefore the analysis is performed using the version of RAM36 coded which includes the treatment of the nuclear quadrupole hyperfine structureIlyushin, V.V. et al, 2010, J. Mol. Spectrosc. 259, 26 The first spectroscopic results will be presented. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.

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Footnotes:

Hollis, J. M.; et al., 2006, ApJ 642, 933p Rubin, R. H. ; et al., 1971, ApJ 169, L39. Kaushik V. K. ; et al., 1978, J. Phys. Soc. Jap. 45, 1975

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Footnotes:

Zou L.; et al., 2019, 74^th ISMS, Champaign USA FB04. Ilyushin, V.V. et al, 2010, J. Mol. Spectrosc. 259, 26.

The study of not only amino acids but its most essential isomers should be of crucial importance for revealing the chemical processes that may have led to life's origin. We here report the first structural characterization of acetohydroxamic acid (CH₃CONHOH), a glycine isomer, using a battery of state-of-the-art rotational spectroscopic techniques in the time domain. The ¹⁴N nuclear quadrupole hyperfine structure and the A-E splittings due to the internal rotation have been observed and analyzed. Hence, a precise set of the rotational spectroscopic parameters have been determined for the two distinct structures, Z-amide and E-amide acetohydroxamic acid, which is the initial and prerequisite step of its radio astronomical search in low-frequency regions.

• Acknowledgments: The authors thank the financial fundings from Ministerio de Ciencia e Innovacion (CTQ2016-76393-P and PID2019-111396GB-I00), Junta de Castilla y Leon (VA077U16 and VA244P20) and European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC-2013-SyG, Grant Agreement n. 610256 NANOCOSMOS, are gratefully acknowledged. M.S.N. acknowledges funding from the Spanish "Ministerio de Ciencia, Innovación y Universidades" under predoctoral FPU Grant (FPU17/02987).

Cysteamine (NH₂CH₂CH₂SH), is the precursor of cysteine (a sulfur-containing amino acid) in cell metabolism. As such it is interesting from the chemical and biochemical point of view and as a target interstellar molecule which could be a precursor of amino acid formation. Its rotational spectrum has already been investigated in the 18-40 GHz frequency region and two conformers and their vibrational satellites were characterized, but the sparse frequency coverage prevents their accurate predictions in higher frequency ranges. Moreover, conformational potential energy scans performed at the B3LYP-GD3(BJ)/def2-TZVP level of calculation suggest the existence of more stable conformers. To fill the lack of its spectroscopic knowledge, we have investigated the pure rotational spectrum of cysteamine by means of a Pulsed Jet Fourier transform microwave spectrometer and a Stark modulated free-jet millimeter-wave absorption spectrometer with frequency ranges of 6.5-18 GHz (46.12-16.66 mm) and 59.6-110.0 GHz (5.03-2.72 mm), respectively. According to theoretical predictions, five conformers, belonging to the gauche skeletal arrangement ( NCCS ≈ 60^°) have been observed, and for three of them also the ³⁴S isotopologues were observed in natural abundance. Some of the detected lines shown a hyperfine structure (∆ν ≤ 1 MHz) due to the nuclear quadrupole interaction of the ¹⁴N atom. Altogether, 336 transition lines of the five parent species and 63 lines of the three ³⁴S isotopologues conformers were assigned to fit the rotational constants, quartic centrifugal distortion constants and the ¹⁴N nuclear quadrupole coupling constants. New laboratory data of cysteamine provided very precise values of the spectroscopic constants that can be used to search for cysteamine in astronomical surveys. As a first try, we have looked towards the north core of the giant molecular cloud Sagittarius B2 (N) (Sgr B2(N)), in the band 3 (3.6-2.6 mm), exploiting Belloche's data stored in the public available Atacama Large Millimeter/submillimeter Array (ALMA) archive (project 2016.1.00074.S).

Pure rotational spectrum of 5-methyl hydantoin (5-methyl-imidazolidine-4-one, C₄H₆N₂O₂), known as a direct precursor of the simplest chiral amino acid Alanine, in its vibrationally excited states were measured in the frequency region of 90-180 GHz. So far, more than 500 spectral lines were recorded, and have been found to be attributed to 4 vibrational states. Guided with the results of density functional theory calculations as well as spectral intensities relative to that of the ground vibrational state, these 4 states can be assigned to fundamental bands and/or combination of these bands whose vibrational energies are considered to be less than 200 cm⁻¹. We also found that transition frequencies for one vibrational excited state can be explained within microwave spectroscopic precision by including the same set of centrifugal distortion constants as those for the ground vibrational sate. While the other spectral line frequencies showed sizeable deviations despite of inclusion of higher-order (up to the 10th order) centrifugal distortion constants. We are currently trying to conduct a perturbation analysis for these data.

The millimeter spectrum of allylimine has been recorded between 80 and 300 GHz with a frequency-modulation absorption spectrometer. Two conformers, syn and anti, have been observed in the gas-phase products of the pyrolysis of diallylamine at 500^°C. The analysis of an extended data set allowed us to determine rotational constants and centrifugal distortion terms up to the sixth power of the angular momentum operators with high accuracy. The new set of spectroscopic constants has been used to search for allylimine signatures in the spectral survey of the quiescent giant molecular cloud G+0.693-0.027, nearby the Galactic center. A tentative detection of both allylimine conformers is reported.

S-type stars are characterized by the presence of ZrO electronic transitions. Analysis of several ZrO band systems has, to date, relied upon data collected using photographic plates and has escaped a more modern spectral analysis made possible with programs such as PGOPHER. We present a re-analysis of a number of vibrational bands associated with the B ¹Π - X ¹Σ⁺ transition based on a high resolution (0.04 cm⁻¹) Fourier transform emission spectrum collected at the National Solar Observatory by S. Davis. The ZrO source was a carbon tube furnace at 2390 K. Updated spectroscopic constants are presented and discussed.

The millimeter-wave spectrum of the SiP radical in its X²Π_i ground electronic state has been recorded using direct absorption spectroscopy in the frequency range 151 – 532 GHz. The species was synthesized in an AC discharge by the reaction of SiH₄ and red phosphorous, in argon carrier gas. Both lambda-doubling and hyperfine splittings, from the phosphorus nuclear spin (I = 1/2), were observed in both spin-orbit ladders, Ω = 3/2 and 1/2. The Ω =1/2 ladder appears to be perturbed, presumably by the nearby A²Σ state, as suggested by previous optical data. The data were analyzed with a Hund’s case (a) Hamiltonian, establishing global spectroscopic constants. A deperturbation analysis was also conducted, further refining the Π-Σ interaction.

Oxiranecarbonitrile (cyano-oxirane, c-C₂H₃OCN) is of interest as a possible chiral precursor molecule of evolutionM. Bolli, R. Micura, A. Eschenmoser, Chem. Biol., 1997, 4, 309 (and refs. cited therein).. We have calculated parity violation in this molecule in view of possible experiments and biomolecular homochiralityR. Berger, M. Quack, G. Tschumper, Helv. Chim. Acta., 2000, 83, 1919; M. Quack, Chem. Phys. Lett. 1986, 132, 147; M. Quack, Angew. Chem. Intl. Ed., 2002, 41, 4618.. Its spectrum has been investigated in the millimeter, submillimeterM. Behnke, I. Medvedev, M. Winnewisser, F. C. De Lucia, and E. Herbst, ApJ. Supplement Series, 2004, 152, 97. and terahertzS. Albert, Ph. Lerch, K. Keppler and M. Quack, Proceedings of the XX. Symposium on Atomic, Cluster and Surface Physics 2016, (SASP 2016), Innsbruck University Press (2016), pp. 165-168 (and refs. cited therein). regions. We have recorded its infrared spectrum at 295K with resolution 0.0011 cm⁻¹using the Zurich Prototype ZP 2001 FTIR spectrometer S. Albert, K. Albert and M. Quack, Trends in Optics and Photonics, 2003, 84, 177; "Handbook," Vol. 2, pp. 965−1019 (see also f).. We report here the results of the rovibrational analysis transitions associated with the ν₁₂ (915.3 cm⁻¹) and ν₁₃ (848.2 cm⁻¹) fundamentals using a Watson Hamiltonian and the WANG programD. Luckhaus and M. Quack, Mol. Phys., 1989, 68, 745; S. Albert, K. Keppler Albert, H. Hollenstein, C. Manca Tanner, M. Quack in "Handbook of High-Resolution Spectroscopy," M. Quack and F. Merkt, Eds., 2011, Vol. 1, Chapter 3, pp. 117-173, Wiley, Chichester., including molecular parameters and ground state energies from our work in the THz region^d. Simulations performed using the parameters reproduce the observed spectrum well. The results are discussed in relation to astrophysical spectroscopic searches and the evolution of biomolecular homochirality R. Berger, M. Quack, G. Tschumper, Helv. Chim. Acta., 2000, 83, 1919; M. Quack, Chem. Phys. Lett. 1986, 132, 147; M. Quack, Angew. Chem. Intl. Ed., 2002, 41, 4618.S. Albert, Ph. Lerch, K. Keppler and M. Quack, Proceedings of the XX. Symposium on Atomic, Cluster and Surface Physics 2016, (SASP 2016), Innsbruck University Press (2016), pp. 165-168 (and refs. cited therein).D. Luckhaus and M. Quack, Mol. Phys., 1989, 68, 745; S. Albert, K. Keppler Albert, H. Hollenstein, C. Manca Tanner, M. Quack in "Handbook of High-Resolution Spectroscopy," M. Quack and F. Merkt, Eds., 2011, Vol. 1, Chapter 3, pp. 117-173, Wiley, Chichester.

Interstellar deuterated cyanoacetylene (DC₃N) has been identified in a vast variety of astronomical sources thanks to the emission of its rotational transitions. To date, the rotational spectrum of DC₃N has been accurately studied in laboratory, while the high-resolution infrared spectrum is limited to the low frequency range (200-1100 cm⁻¹). In order to support the identification of DC₃N in different spectral regions, we have investigated the infrared spectrum of DC₃N in the stretching region (1500-3500 cm⁻¹). The ν₁, ν₂, and ν₃ fundamentals as well as their hot-bands were recorded at 0.004 cm⁻¹ resolution using a Fourier transform infrared spectrometer. Additional pure rotational spectra in the v₃ = 1, v₂ = 1, and v₃ = v₇ = 1 vibrational excited states were observed between 243 and 295 GHz with a frequency-modulation millimeter/submillimeter-wave spectrometer equipped with an electric furnace. The precision of the pure rotational lines, intrinsically much higher than ro-vibrational data, allowed us to improve the accuracy of the upper state spectroscopic parameters. The rotational and ro-vibrational data of DC₃N were combined into a single fit from which a consistent set of spectroscopic constants has been determined. In addition, the ro-vibrational features of its parent species (HC₃N) have been analyzed as well because HC₃N is observed as a by-product in the same spectra. The result of the combined analysis provides a highly-precise rest-frequency catalog that can be used to model the infrared spectra of DC₃N and HC₃N. r0pt Figure

Iron monohydride, FeH, is an important astrophysical molecule observed in the cool outer layers of stellar atmospheres. It has a strong magnetic response, which leads to pronounced Zeeman splitting of its spectral lines. Such splitting is observed in spectra of FeH taken above sunspots on the Sun, where magnetic fields are strong. Therefore, a thorough understanding of the structure of FeH and of its Zeeman response provides a way to make excellent measurements of the Sun’s magnetic field in the region of sunspots. The parent isotopologue FeH has been extensively studied, notably by the group of J. M. Brown (see J. Chem. Phys. 121 (2004) 7335 and references therein). However, the deuterated isotopologue, FeD, has received scant attention. We have undertaken a series of experiments on FeD, which we create from the reaction of Ar+D₂ discharge products with iron pentacarbonyl, Fe(CO)₅. The FeD molecules are probed with light from a scanning cw ring dye laser with laser excitation spectroscopy. Furthermore, with the laser frequency fixed to excite a single upper-state level we also dispersed the fluorescence at high resolution with a Bomem Fourier transform spectrometer. We have been able to characterize 5 excited electronic states of FeD for the first time. The new data greatly extend our understanding the FeH/FeD system as a whole.

Quantifying molecular abundances of astrochemical species is a key step towards the understanding of the chemistry occurring in the interstellar medium. This process requires a profound knowledge of the molecular energy levels, including their structure resulting from weak interactions between nuclear spins and the molecular rotation. With the aim of increasing the quality of spectral line catalogs for the singly- and doubly-deuterated ammonia (NH₂D and ND₂H), we have revised their rotational spectra by observing many hyperfine-resolved lines and more accurate high-frequency transitions. The measurements have been performed in the submillimeter-wave region (265-1565 GHz) using a frequency modulation submillimeter spectrometer and in the far-infrared domain (45-220 cm⁻¹) with a synchrotron-based Fourier-transform interferometer. The analysis of the new data, with the interpretation of the hyperfine structure supported by state-of-the-art quantum-chemical calculations, led to an overall improvement of all spectroscopic parameters. Moreover, the effect of the inclusion of deuterium splittings in the analysis of astrophysical NH₂D emissions at millimeter wavelengths has been tested using recent observations of the starless core L1544, an ideal astrophysical laboratory for the study of deuterated species. Our results show that accounting for hyperfine interactions leads to a small but significant change in the physical parameters used to model NH₂D line emissions.