The spectra of ZrO molecules are prominent in the near infrared and optical spectra of S-type stars. S-type stars have approximately equal carbon and oxygen abundances. We have analyzed the B¹ Π− X¹ Σ⁺, C¹ Σ⁺ − X¹ Σ⁺, and B¹ Π− A¹ ∆ electronic transitions of ZrO. The emission spectrum was collected from a high temperature (2405 K) carbon furnace at the National Solar Observatory (Kitt Peak). The rotational analysis was performed using the PGOPHER program to provide spectroscopic constants. These constants were used to calculate line lists with intensities obtained from ab initio transition dipole moments.

Diffuse interstellar bands (DIB), narrow absorption features observed from the near IR to the UV, have drawn a lot of interest since their first discovery in 1922. Polycyclic aromatic hydrocarbons (PAH) and their cationic, protonated and hydrogenated derivatives are considered particularly promising candidates for the DIB carriers, but laboratory spectra of these unstable species suitable for comparison to astronomical observations are scarce. para-Hydrogen (para-H₂) matrix isolation spectroscopy has frequently been employed to record the IR spectra of PAH derivatives. The obtained spectra exhibit only small shifts in line positions due to small interactions with the matrix host, in line with the ‘softness’ of the quantum solid para-H₂. However, electronic spectra of PAH isolated in solid para-H₂ have rarely been reported. Ovalene (C₃₂H₁₄) and peri-hexabenzocoronene (HBC, C₄₂H₁₈) have both been discussed as potential DIB carriers and, therefore, their electronic absorption spectra have been studied in the gas-phase and in rare gas matrices. To assess the properties of para-H₂ as a matrix host for electronic spectroscopy, we present the fluorescence excitation and dispersed fluorescence spectra of these two large PAH isolated in solid para-H₂. We located the 0₀⁰ bands of the S₁–S₀ transitions at 21049 cm⁻¹and about 22075 cm⁻¹for ovalene and HBC, respectively. The recorded excitation spectra in general show a good agreement with previously reported absorption spectra indicating a matrix shift below 100 cm⁻¹due to the para-H₂ matrix host, consistent with our earlier experiments on several smaller PAH. We complemented our experimental work with Franck-Condon Herzberg-Teller simulations on the basis of optimized geometries and vibrational frequencies obtained from (TD-)DFT calculations to derive a first assignment of individual vibrational modes to the observed absorption and emission bands associated with the electronic S₁–S₀ transition. For ovalene, we find that a consideration of the closely lying S₂ state is required to reproduce the complexity of the experimental excitation spectrum by the simulation.

Organohalogen molecules are important reactants in Earth’s atmosphere contributing to ozone layer loss. The simplest oxygen bearing organochloride, methyl hypochlorite CH₃OCl, is expected as a product in ozone hole chemistry. Interstellar chemistry of organohalogens has received recent interest through the detection of the methylchloride, while searches for more complex organochlorides is limited due to lack of available spectra. We synthesized and recorded the submillimeter wave spectrum of methyl hypochlorite between 150-500 GHz using absorption spectroscopy. The fitted spectra are extended for both chlorine isotopologues, with hyperfine structure present to high frequencies. The details of the spectroscopic analysis and prospects for detection in space will be discussed.

3-Hydroxypropenal is the lower energy tautomeric form of propanedial, also known as malonaldehyde. It has two equivalent minima separated by a modest barrier which leads to two tunneling states separated by 647 GHz. Its rotational spectrum was analyzed in several studies, most recently through its a-type rotation-tunneling spectrum near 650 GHz.T. Baba et al., J. Chem. Phys. 110 1999, 4131.-Hydroxypropenal was identified tentatively within the framework of the Protostellar Interferometric Line survey (PILS) toward the prototypical solar-type Class 0 young stellar system IRAS 16293−2422 carried out with the Atacama Large Millimeter/submillimeter Array (ALMA).A. Coutens et al., Astron. Astrophys. 660 2022, L6.he conclusions drawn from this study were severely limited by the fact that the rest frequencies of many potentially observable transitions were so uncertain that they could not be identified unambiguously. We have analyzed spectral recordings of 3-hydroxypropenal taken in LilleThis work was supported by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNEShat cover large parts of the 150−660 GHz region to overcome these limitations. We will present our results and the astronomical implications.

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T. Baba et al., J. Chem. Phys. 110 1999, 4131.3 A. Coutens et al., Astron. Astrophys. 660 2022, L6.T This work was supported by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNESt

Maleonitrile (N ≡ C-CH=CH-C ≡ N) is a complex organic molecule (COM) isoelectronic to the trans-cyanovinylacetylene (H-C ≡ C-CH=CH-C ≡ N), which has been recently detected in the interstellar medium (ISM) towards the dark molecular cloud TMC-1.Lee K.L.K. et al., ApJL, 908, L11, 2021oth structures only differ from the ubiquitous vinyl cyanide (H-CH=CH-C ≡ N) by replacing one of the terminal hydrogens by a nitrile or acetyl group. The generation of maleonitrile and trans-cyanovinylacetylene in the space might follow similar synthetic routes. However, the lack of precise rotational constants for maleonitrile, only studied up to 15GHz,Halter, R.J., et al., J. Am. Chem. Soc., 123, 49, 12353–12363, 2019amper its detection in the space. In the present work, our goal is, firstly, to provide a complete and precise set of rotational parameters for maleonitrile and, finally, to search for in the interstellar medium. For its rotational analysis we have employed the broadband millimeterwave spectrometer based on radioastronomical receivers GACELA (GAs CEll for Laboratory Astrophysics) working in the W band (72-116.5 GHz). Cernicharo, J. et al. A&A, 626, A34 2019he rotational spectra of maleonitrile have been analyzed for the ground state, and the first vibrational excited states: ν₇, 2ν₇, ν₁₀ and ν₁₈. All of them with energy bellow 300cm⁻¹. A total of 537, 318, 55, 64 and 63, respectively, pure rotational transitions have been included in the fit. Maleonitrile was search in the space towards the TMC-1 molecular cloud.

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Lee K.L.K. et al., ApJL, 908, L11, 2021B Halter, R.J., et al., J. Am. Chem. Soc., 123, 49, 12353–12363, 2019h Cernicharo, J. et al. A&A, 626, A34 2019T

Over 250 distinct chemical species have been detected in the interstellar regions of space. The harsh conditions of astrophysical objects mean that the molecules that form and evolve there are not subject to the same reaction conditions as on Earth. The products formed upon UV excitation of methanol, an extremely prevalent molecule in space, have not been well constrained. In a collaborative project between UMD and two government research labs—Sandia National Laboratories and Lawrence Berkeley National Laboratory—we carried out UV photodissociation studies on gas-phase methanol using 193 nm light at the Advanced Light Source synchrotron. We have identified and quantified the photodissociation products and their associated branching ratios via Multiplexed Photoionization Mass Spectrometry. Empowered by the tunability of the synchrotron source, isomeric products such as CH₃O/CH₂OH and HCOH/H₂CO were able to be differentiated at different ionization energies, providing a more complete understanding of each species independently. The results of this work will inform astronomers of the destruction processes possible for this important astrochemical in regions of space with high ultraviolet radiation fields.

Thiocyanates (RSCN) are not only important for their implication in functional materials and pharmaceutical chemistry, but also as potential candidates to be present in the interstellar medium (ISM). In fact, thiocyanic acid (HSCN)Brunken, S. et al. (2009) ‘LABORATORY DETECTION OF THIOCYANIC ACID HSCN’, The Astrophysical Journal. IOP Publishing, 706(2), p. 1588. doi: 10.1088/0004-637X/706/2/1588.Halfen, D. T. et al. (2009) ‘DETECTION OF A NEW INTERSTELLAR MOLECULE: THIOCYANIC ACID HSCN’, The Astrophysical Journal. IOP Publishing, 702(2), p. L124. doi: 10.1088/0004-637X/702/2/L124. and its isomer isothiocyanic acid (HNCS)Frerking, M. A., Linke, R. A. and Thaddeus, P. (1979) ‘Interstellar isothiocyanic acid’. United States, 234:2. doi: 10.1086/183126.ave already been detected. It is a logical step to keep studying more complex molecules of the same family, also to shed light on the sulphur chemistry in the ISM. Microwave and millimetre-wave spectroscopy are the ultimate tools that enable the detection of molecular systems in the ISM. Here we present a challenging laboratory characterization of the simplest alkynyl thiocyanate HCCSCN in the microwave and millimetre-wave ranges. Results of this work will allow to search for HCCSCN in different regions of the ISM.

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Footnotes:

Brunken, S. et al. (2009) ‘LABORATORY DETECTION OF THIOCYANIC ACID HSCN’, The Astrophysical Journal. IOP Publishing, 706(2), p. 1588. doi: 10.1088/0004-637X/706/2/1588.

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Footnotes:

Frerking, M. A., Linke, R. A. and Thaddeus, P. (1979) ‘Interstellar isothiocyanic acid’. United States, 234:2. doi: 10.1086/183126.h

Wing cut-off dictates the frequency extent to which the Lorentzian line wings are computed from the line core. Establishing a consistent policy for determining the limit of the extent of the line profile is a difficult and complex problem. For any given species a knowledge of the true shape of the line wing usually defined as the region beyond a certain multiple of the line width of the central core may not be well established either by theory, experiment, or a combination of the two. Inaccuracy in the wing cut-off results in up to a few magnitudes of error in the opacity continuum and biases the modeled transmission and emission spectra, and ultimately impacts/biases the interpretation of observational spectra and the derived composition and thermal structure. Uncertainties in the calculation of absorption cross-section data in far wings and the line shape spectroscopic parameters for high pressures ( > 100 atm) are among those challenges that should be considered for generating accurate data for atmospheric radiative transfer modeling studies. In this talk, our community efforts to address these issues will be presented.

Recent observations of the evolved carbon star IRC+10216 with unprecedented high angular resolution have revealed a plethora of unassigned (U) rovibrational lines associated with the dust formation zone. Because SiC₂ is a known, abundant molecular constituent of this region, it is a reasonable supposition that some fraction of the observed U lines arise from vibrationally excited levels of SiC₂ populated at elevated temperatures. At present, the laboratory rotational data that would permit testing of this hypothesis are largely absent: ab initio prediction of relevant spectroscopic constants has proved particularly challenging for SiC₂, and its excited vibrational levels are not efficiently populated in supersonic jet sources. However, the electronic transition responsible for the well-known blue-green Merrill-Sanford bands of SiC₂ admits Franck-Condon access to vibrational levels at least 4000 K above ground, inviting the application of SEP spectroscopy for the observation of vibrationally excited states. SiC₂ has been generated in our laboratory in a jet-cooled discharge of silane and acetylene, optically pumped via the M-S bands, and fluorescence depletion SEP spectra observed for dump transitions terminating in a variety of excited rovibrational levels for all three modes in the X̃-state. For known rotational levels of 1ν₃ and 2ν₃ (the pinwheel mode), the rotational energies derived from SEP spectra are in generally excellent agreement (a factor of at least 5 smaller than the dump laser linewidth) with previous observations, giving us good faith in our experimental procedure. The 1ν₂ level is notably perturbed, which likely accounts for its as-yet non-observation in the laboratory by rotational spectroscopy. A Fermi resonance with 6ν₃ depresses the 1ν₂ B and C constants significantly below the predictions of high-level theory. Vibrationally averaged rotational constants calculated using Fermi resonance mixing coefficients obtained from Ã-state zero-point dispersed fluorescence are broadly consistent with this interpretation.