The rotational spectrum of the chiral mono-deuterated oxirane c-C₂H₃DO, an isotopomer of oxirane (ethylenoxide), of which the normal isotopomer has already been detected in interstellar clouds, was measured in the ranges 78 to 108 GHz and 25 to 70 cm⁻¹. Thus one can expect that c-C₂H₃DO will be detectable in space in the future given the current accurate laboratory data.c-C₂H₃DO is also of interest as a simple prototypical molecule for isotopic chirality and parity violation.M. Quack, Angew. Chem. Int. Ed. 28, 571-586 (1989)._'M. Quack , Fundamental Symmetries and Symmetry Violations from High-resolution Spectroscopy, Handbook of High Resolution Spectroscopy, M. Quack and F. Merkt eds.,John Wiley & Sons Ltd, Chichester, New York, 2001, vol. 1, ch. 18, pp. 659−722._′R. Berger, G. Laubender, M. Quack, A. Sieben, J. Stohner and M. Willeke, Angew. Chem. Int. Ed. 44, 3623-3626 (2005)._'S. Albert, I. Bolotova, Z. Chen, C. Fábri, L. Horný, M. Quack, G. Seyfang and D. Zindel, Phys.Chem.Chem.Phys.18, 21976−21993 (2016)._′ The Zurich GHz spectrometer and a high resolution FTIR interferometer using synchrotron radiation was used for the THz spectrum.^d_′S. Albert, I. Bolotova, Z. Chen, C. Fábri, L. Horný, M. Quack, G. Seyfang and D. Zindel,Proceedings of the 20th Symposium on Atomic, Cluster and Surface Physics (SASP 2016), Innsbruck University Press, 2016, pp. 127-130, ISBN:978-3-903122-04-8. and to be published._' M. Quack , Fundamental Symmetries and Symmetry Violations from High-resolution Spectroscopy, Handbook of High Resolution Spectroscopy, M. Quack and F. Merkt eds.,John Wiley Sons Ltd, Chichester, New York, 2001, vol. 1, ch. 18, pp. 659-722.S. Albert, I. Bolotova, Z. Chen, C. Fbri, L. Horn, M. Quack, G. Seyfang and D. Zindel, Phys.Chem.Chem.Phys.18, 21976-21993 (2016).S. Albert, F. Arn, I. Bolotova, Z. Chen, C. Fbri, G. Grassi, Ph. Lerch, M. Quack, G. Seyfang, A. Wokaun and D. Zindel, J.Phys.Chem.Lett,7, 3847-3853 (2016).P

Methyl formate (HCOOCH₃) is an abundant interstellar molecule, found almost everywhere in the star-forming region. The interstellar abundance of the ¹³C is about 1/50 of ¹²C. The ¹³C substituted methyl formate in the ground and first excited states were already found toward massive star-forming regions including Orion KL.

Recent detection of methyl isocyanate (CH₃NCO) in the OrionJ. Cernicharo, N. Marcelino, E. Roueff et al. 2012, ApJ, 759, L43 towards Sgr B2(N)D. T. Halfen, V. V. Ilyushin, & L. M. Ziurys, 2015, ApJ, 812, L5 nd on the surface of the comet 67P/Churyumov-GerasimenkoF. Goesmann, H. Rosenbauer, J. H. Bredehöft et al. 2015, Science, 349.6247, aab0689otivated us to study another isocyanate, methoxy isocyanate (CH₃ONCO) as a possible candidate molecule for searches in the interstellar clouds. Neither identification or laboratory rotational spectra of CH₃ONCO has been reported up to now. Methoxy isocyanate was synthesized by the flash vacuum pyrolysis of N-Methoxycarbonyl-O-methyl-hydroxylamine (MeOC(O)NHOMe) at a temperature of 800 K. Experimental spectrum of CH₃ONCO was recorded in situ in the millimeter-wave range (75-105 GHz and 150-330 GHz) using Lille's fast-scan fully solid-state DDS spectrometer. The recorded spectrum is strongly perturbed due to the interaction between the overall rotation and the skeletal torsion. Perturbations affect even rotational transitions with low K_a levels of the ground vibrational state, appearing in shifting frequency predictions and intensities distortions of the lines. The interactions are significant due to the relatively small vibrational energy difference ( ≈ 50 cm⁻¹) between the states and different representations of the C_s symmetry point group for the ground (A′), ν₁₈=1 (A") and ν₁₈=2 (A′) vibrational states, thus leading to a “ladder" of multiple resonances by means of a-, and b-type Coriolis coupling. The global fit analysis of the rotational spectrum of methoxy isocyanate using Coriolis coupling terms in the ground and two lowest vibrational states (ν₁₈=1 and ν₁₈=2) will be presented. This work was funded by the French ANR under the Contract No. ANR-13-BS05-0008-02 IMOLABS.

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J. Cernicharo, N. Marcelino, E. Roueff et al. 2012, ApJ, 759, L43, D. T. Halfen, V. V. Ilyushin, & L. M. Ziurys, 2015, ApJ, 812, L5 a F. Goesmann, H. Rosenbauer, J. H. Bredehöft et al. 2015, Science, 349.6247, aab0689m

We have performed a study of the millimeter/submillimeter wave spectrum of four higher energy conformers of 1,2-propanediol (continuation of the previous study on the three lowest energy conformersJ.-B. Bossa, M.H. Ordu, H.S.P. Müller, F. Lewen, S. Schlemmer, A&A 570 (2014) A12. The present analysis of rotational transitions carried out in the frequency range 38 – 400 GHz represents a significant extension of previous microwave work. The new data were combined with previously-measured microwave transitions and fitted using a Watson’s S-reduced Hamiltonian. The final fits were within experimental accuracy, and included spectroscopic parameters up to sixth order of angular momentum, for the ground states of the four higher energy conformers following previously studied ones: g′Ga, gG′g′, aGg′ and g′Gg. The present analysis provides reliable frequency predictions for astrophysical detection of 1,2-propanediol by radio telescope arrays at millimeter wavelengths.

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J.-B. Bossa, M.H. Ordu, H.S.P. Müller, F. Lewen, S. Schlemmer, A&A 570 (2014) A12)

Methanol, a ubiquitous molecule in the interstellar medium (ISM), has an important role in the production of more complex organic molecules (COMs) in both grain-surface and gas-phase interstellar chemistry. Some of the direct products of methanol photolysis, including radicals such as methoxy, hydroxymethyl, hydroxyl, and methyl, are believed to directly influence the relative abundances of important COMs that are both detected and theorized to be in the ISM. However, no laboratory study has been performed to date which has determined the individual branching ratios of these photolysis products, because many of the channels cannot be distinguished using traditional techniques. To address this problem, we used a 193 nm excimer laser to photolyze methanol in the throat of a supersonic expansion, and probed the resultant products using a millimeter/submillimeter direct absorption spectrometer. Each product channel has a unique rotational spectrum, allowing quantitative density and temperature information to be determined. This information can in turn be used to calculate the full set of branching ratios for methanol photolysis. In this talk we will present the results of this experiment and discuss the implications for astrochemistry.

The relevance of interstellar ice to the chemical complexity of the interstellar medium has dramatically increased over the past 15 years. Previous astrochemical models including only gas-phase reactions were unable to explain the abundances of many complex organics observed in the interstellar medium. To correct for this, current models have added grain-surface chemistry as a source for some organic molecules that serve as building blocks to biologically-relevant complex organic compounds. We have therefore built a new experiment to investigate the gas-phase chemistry above interstellar ice analogs during thermal and photoprocessing using millimeter/submillimeter spectroscopy. Our first experiments have focused on pure methanol ices to 1) demonstrate this unique technique 2) optimize the experiment and 3) to compare our results with recent work by Cruz-Diaz et al. and Beltran et al. and do further analysis of products they are unable to measure (e.g. isomers CH3O and CH2OH). We have detected CO as a major product of methanol photoprocessing. But it is unclear from our initial results how the formation and photodesorption of CO from methanol ice is related to the ice temperature during the photoprocessing. We have therefore conducted two experiments: simultaneous photoprocessing and thermal desorption, and photoprocessing at a low temperature followed by temperature programmed desorption to liberate the CO. The initial results from both of these experiments will be presented in this talk, as well as the implications of these results for astrochemistry.

Small silicon and carbon containing molecules are thought to be important building blocks of interstellar grains. Some of them have been detected in circumstellar environments of late-type stars by means of rotational spectroscopy e.g., SiC, SiC₂, Si₂C, c-SiC₃, SiC₄, while centro-symmetric species, e.g., C₃, C₄, C₅, Si₂C₂, Si₂C₃, can only be detected by vibrational transitions, mainly in the infrared. In view of a new generation of high resolution infrared telescope instruments, e.g., EXES (Echelon-Cross-Echelle Spectrograph) onboard SOFIA (Observatory for Infrared Astronomy) and TEXES (Texas Echelon Cross Echelle Spectrograph) at the Gemini-North observatory, accurate laboratory data of small silicon-carbides in the infrared region are of high demand. In this talk we present first laboratory data of the Si₂C asymmetric stretching mode at 1200 cm⁻¹. A pulsed Nd:YAG-laser is used to vaporize a solid target of silicon exposed to a dilute sample of methane in helium buffer gas. Si₂C is formed in an adiabatic expansion of a supersonic jet and radiation of a quantum cascade laser is used to record rotationally resolved spectra. To date, 160 ro-vibrational lines and have been assigned to the asymmetric stretching vibration of Si₂C, and derived molecular parameters are in excellent agreement with ab initio calculations. In our global fit analysis recently published microwave laboratory data (McCarthy et al. 2015)McCarthy M.C., Baraban J.H., Changala P.B., Stanton J.F., Martin-Drumel M.A, Thorwirth S., et al., J. Chem. Phys. Lett. 6, 2107–2111 (2015).nd astronomical data (Cernicharo et al. 2015)Cernicharo J., McCarthy M.C., Gottlieb C.A., Agundez M., Velilla Prieto L., Baraban J.H., et al. Astrophys. J. Lett. 806,L3 (2015).ere taken into account. Our new results allow for the identification of Si₂C by means of high resolution infrared astronomy towards the warm background of carbon-rich stars.

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McCarthy M.C., Baraban J.H., Changala P.B., Stanton J.F., Martin-Drumel M.A, Thorwirth S., et al., J. Chem. Phys. Lett. 6, 2107–2111 (2015).a Cernicharo J., McCarthy M.C., Gottlieb C.A., Agundez M., Velilla Prieto L., Baraban J.H., et al. Astrophys. J. Lett. 806,L3 (2015).w

The OH⁺ ion is an important species in the Interstellar Medium. It has been used to infer the cosmic ray ionization rate and is an important intermediate for generation of more complex astrochemical species. OH⁺ observations are typically performed in the sub-millimeter and near-UV ranges, and rely on laboratory spectroscopy to provide transition frequencies. Observations of the A³Π−X³Σ⁻ bands are used to both identify OH⁺ and determine the column densities along sight lines.Zhao, D. et al. 2015, ApJ, 805, L12hese A-X observations have relied on previous measurements with a grating spectrometer and photographic plates.Merer, A.J. et al. 1975, CaJPh, 53, 251ere, we present data recorded at Kitt Peak using a Fourier transform spectrometer of the A-X band system. This data and other available data are combined to determine new molecular constants for the A and X electronic states. These new data are between one and two orders of magnitude more precise and should be used in support of observations in lieu of the older transition frequencies. We also intend to calculate improved line intensities in support of astronomical observations.

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Zhao, D. et al. 2015, ApJ, 805, L12T Merer, A.J. et al. 1975, CaJPh, 53, 251H

Pluto is a large icy body composed of N₂, CH₄, and H₂O ices. In many ways, Pluto can be seen as one large matrix isolation experiment where N₂ is the inert matrix that can act to trap and isolate reactive species. The temperature changes on the dwarf planet induce sublimation of N₂ from the surface. Any previously trapped reactive species could then react with the new ice or neighboring molecules. To see if this process might lead to a significant formation of molecules, Fourier-Transform Infrared (FTIR) Spectroscopy (4 cm⁻¹ resolution) was used to study and monitor the sublimation of ices created from irradiated gas mixtures of 1:1:100 CO+H₂O+N₂ or 1:1:100 CH₄+H₂O+N₂. The gas mixtures were initially prepared and deposited on a cold finger at a temperature of 6 K and a baseline vacuum of about 1 x 10⁻⁷ Torr. Gas mixtures were irradiated using an electric discharge or a microwave discharge before deposition to create the unstable chemical species. To sublimate the matrix, the temperature was brought up step-wise in 5-10 K intervals to 45 K. Slow sublimation (10 min per step) resulted in the new species being trapped in a water ice. In addition to (FTIR) spectroscopy, chemical species were also identified or monitored using ultraviolet-visible (UV-Vis) spectroscopy and a residual gas analyzer (RGA). Carbon suboxide (C₃O₂), a common component found in meteorites and a potentially important prebiotic molecule, was formed only after the sublimation step. Other products formed included deprotonated versions of products formed in the original matrix ice. C₃O₂’s potential importance in Pluto’s surface chemistry and its overall astrobiological significance will be discussed.

The [NH₂, C, N, O] and the [NH₂, C, N, S] systems were investigated by quantum-chemical computations and matrix-isolation spectroscopic methods. The equilibrium structures of the isomers and their relative energies were determined by CCSD(T) method. This was followed by the computation of the harmonic and anharmonic vibrational wavenumbers, infrared intensities, relative Raman activities and UV excitation energies. These computed data were used to assist the identification of products obtained by UV laser photolysis of 3,4-diaminofurazan, 3,4-diaminothiadiazole and 1,2,4-thiadiazole-3,5-diamine in low-temperature Ar and Kr matrices.T. Voros, Gy. Gy. Lajgut, G. Magyarfalvi, Gy. Tarczay, J. Chem. Phys., 146, 024305, 2017.xperimentally, first the precursors were studied by matrix-isolation IR and UV spectroscopic methods. Based on these UV spectra, different wavelengths were selected for photolysis. The irradiations, carried out by a tunable UV laser-light source, resulted in the decomposition of the precursors, and in the appearance of new bands in the IR spectra. Some of these bands were assigned to cyanamide (H₂NCN) and its isomer, the carbodiimide molecule (HNCNH), generated from H₂NCN. By the analysis of the relative absorbance vs. photolysis time curves, the other bands were grouped to three different species both for the O- and the S-containing systems. In the case of the O-containing isomers, these bands were assigned to the H₂NNCO:H₂NCN, and H₂NCNO:H₂NCN complexes, and to the ring-structure H₂NC(NO) isomer. In a similar way, the complexes of H₂NNCS and H₂NCNS with the H₂NCN, and H₂NC(NS) were also identified. 1,2,4-thiadiazole-3,5-diamine was also investigated in similar way like the above mentioned precursors. The results of this study also support the identification of the new S-containing isomers. Except for H₂NNCO and H₂NCNS, these molecules were not identified previously. It is expected that at least some of these species, like the methyl isocyanate (CH₃CNO) isomerD. T. Halfen, V. V. Ilyushin, L. M. Ziurys, Astrophys. J., 812, L5, 2015.^, J. Cernicharo et. al., Astron. Astrophys., 587, L4, 2016.,

Hydrogenation reactions in the N/O chemical network are important for an understanding of the mechanism of formation of organic molecules in dark interstellar clouds, but many reactions remain unknown. We present the results of the reaction H + HONO in solid para-hydrogen (p-H₂) at 3.3 K investigated with infrared spectra. Two methods that produced hydrogen atoms were the irradiation of HONO molecules in p-H₂ at 365 nm to produce OH radicals that reacted readily with nearby H₂ to produce mobile H atoms, and irradiation of Cl₂ molecules (co-deposited with HONO) in p-H₂ at 405 nm to produce Cl atoms that reacted readily with nearby H₂ to produce mobile H atoms. In both experiments, we assigned IR lines at 3549.6 (ν₁), 1465.0 (ν₃), 1372.2 (ν₄), 895.6/898.5 (ν₆), and 630.9 (ν₇) cm⁻¹to N-oxidohydroxylamine [•ONH(OH)], the primary product of HONO hydrogenation. The assignments were derived according to the consideration of possible reactions and comparison of observed vibrational wavenumbers and their IR intensities with values predicted with the B3LYP/aug-cc-pVTZ method of quantum-chemical calculations. The agreement between observed and calculated D/H- and ¹⁵N/¹⁴N-isotopic ratios further supports these assignments. The role of this reaction in the N/O chemical network in dark interstellar clouds is discussed.

Large protonated polycyclic aromatic hydrocarbons (H⁺PAH) and polycyclic aromatic nitrogen heterocycles (H⁺PANH) have been proposed as possible carriers of unidentified infrared (UIR) emission bands from galactic objects. The nitrogen atom in H⁺PANH is expected to induce a blue shift of the C=C stretching band near 6.2 μm so that their emission bands might agree with the UIR band better than those of H⁺PAH. In this work, we report the IR spectrum of protonated quinoline and its neutral species measured upon electron bombardment during deposition of a mixture of quinoline and para-hydrogen at 3.2 K. New features were assigned to 1-C₉H₇NH⁺ and 1-C₉H₇NH, indicating that the protonation and hydrogenation occur at the N-atom site. The intensities of features of 1-C₉H₇NH⁺ diminished when the matrix was maintained in darkness for 10 h, whereas those of 1-C₉H₇NH increased. Spectral assignments were made according to comparison of experimental results with anharmonic vibrational wavenumbers and IR intensities calculated with the B3LYP/6-311++G(d,p) method. Although agreement between the observed spectrum of 1-C₉H₇NH⁺ and the UIR emission bands is unsatisfactory, presumably because of the small size of quinoline, we did observe C=C stretching bands at 1641.4, 1598.4, 1562.0 cm⁻¹, blue-shifted from those at 1618.7, 1580.8, 1510.0 cm⁻¹of the corresponding protonated PAH (C₁₀H₉⁺), pointing to the direction of the UIR bands.