The role of iron containing molecular species in the interstellar medium is not fully understood. Iron monoxide was tentatively detected toward Sagittarius B2.C.M. Walmsley et al., Astrophys. J., 566:L109-L112, (2002).n the laboratory the isotopologues ⁵⁶FeO and ⁵⁴FeO were rotationally measured in all five spin states in their X⁵∆_i ground state by Allen et al.M.D. Allen et al., Chem. Phys. Lett., 257, 130-136, (1996).e present laboratory measurements of rotational lines of the rare isotopologues ⁵⁷FeO, ⁵⁸FeO, and ⁵⁶Fe¹⁸O, including the hyperfine structure splitting due to the nuclear spin I=1/2 of ⁵⁷Fe. We performed a mass independent analysisA.A. Breier et al., J. Mol. Spectrosc., 355, 46-58, (2019).ith the new isotopic data and data from the literature. This enables us to predict molecular parameters and line transitions of the radioactive isotopologue ⁶⁰FeO. Kami\'nski et al. detected the radioactive molecule ²⁶AlF in the merger CK Vulpeculae by means of rotational spectroscopy T. Kami\'nski et al., Nature Astronomy, 2, 778-783, (2018). This is a powerful novel approach to use molecular transition to search for iron and its isotopes. Iron monoxide is a well suited candidate for a astronomical search for ⁶⁰Fe.

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Footnotes:

C.M. Walmsley et al., Astrophys. J., 566:L109-L112, (2002).I M.D. Allen et al., Chem. Phys. Lett., 257, 130-136, (1996).W A.A. Breier et al., J. Mol. Spectrosc., 355, 46-58, (2019).w T. Kami\'nski et al., Nature Astronomy, 2, 778-783, (2018)..

The divalent tin HSnCl transient molecule has been detected for the first time by LIF spectroscopy. HSnCl and DSnCl were produced in a twin discharge jet using separate precursor streams of SnH₄ and HCl (DCl), both diluted in high pressure argon. The ùA"-~X¹A′ spectrum of HSnCl consists of a single rotationally resolved 0-0 band with a very short fluorescence lifetime ( ∼ 25 ns). In contrast, the spectrum of DSnCl exhibits three bands (0₀ ⁰, 2₀ ¹ and 2₀ ²) whose fluorescence lifetimes decrease from 400 ns (0⁰) to less than 10 ns (2²). Single vibronic level emission spectra have been recorded, providing information on all three vibrational modes in the ground state. Fluorescence hole burning experiments have shown that a few higher nonfluorescent levels are very short-lived but still detectable. Our detailed ab initio studies indicate that these molecules dissociate into SnCl + H on the excited state potential surface and this is the cause of the short fluorescence lifetimes and breaking off of the fluorescence. It is fortunate that the HSnCl excited state zero-point level is still fluorescent or it would not be detectable by LIF spectroscopy. Our calculations also predict that HSnBr should also fluoresce on excitation of low-lying bending levels in the excited state.

HSnBr and DSnBr were produced in a twin discharge jet using separate precursor streams of SnH₄ and HBr (DBr), both diluted in high pressure argon. The ùA"-~X¹A′ band system of HSnBr consists of only three bands (0₀ ⁰, 3₁ ¹ and 2₀ ¹) with fluorescence lifetimes from 560 ns (0⁰) to 38 ns (2¹ K_a=1). The DSnBr molecule shows a more extensive LIF spectrum including a weak 1₀ ¹ band, with an energy 817 cm⁻¹above the zero-point and fluorescence lifetimes ranging from 530 ns (0⁰) to 180 ns (1¹). The ground state vibrational energy levels of both HSnBr and DSnBr have been measured from single vibronic level emission spectra. Our own ab initio studies show that these molecules dissociate into SnBr + H on the excited state potential surface, slightly above the zero-point level, accounting for the lack of detectable fluorescence from higher vibronic levels. Similar studies predict that HSnF should not fluoresce at all and, despite extensive effort, no detectable LIF signals were found in twin discharge jet experiments designed to detect the fluorinated species.

r0pt Figure   The study and analysis of heavy spherical-top molecules is often not straightforward. The presence of hot bands and of many isotopologues can lead to a high line congestion very difficult for assignment. In this work, using a low-order model we have derived very simple isotopic relations in order to determine initial parameters of the analysis. We also show that an identical approach can be used for XY₄ and XY₆ molecules and all these results are illustrated by the comparison of numerical computations and experiments for different molecules: CH₄, GeH₄, RuO₄ (as shown in the figure on the right) and SF₆.   Reference: M. Loëte, C. Richard and V. Boudon, J. Mol . Struct. 1206, 127729 (2020).

Chlorine nitrate (ClONO₂) is a very important atmospheric "reservoir" of ClO and NO₂, destroying stratospheric ozone through catalytic cyclesP. J. Crutzen, Quart. J. Royal Met. Soc. 96, 320 (1970); M. J. Molina and F. S. Rowland, Nature 249, 810 (1974). It was detected for the first time by infrared (IR) spectroscopyD. G. Murcray et al., Geophys. Res. Lett. 6, 857 (1979). a detection confirmed and extended by the MIPASH. Fischer et al., Atmos. Chem. Phys. 8, 2151 (2008).nd the ATMOS satellite experimentsR. Zander et al., Geophys. Res. Lett. 13, 757 (1986). Many high-resolution microwave and mid-IR spectroscopy studies of ClONO₂ have been publishedJ. Orphal, M. Birk, G. Wagner, and J.-M. Flaud, Chem. Phys. Lett. 690, 82 (2017). However, ClONO₂ presents 4 fundamentals in the far-IR region below 600 cm⁻¹, with the lowest one corresponding to the torsional mode ν₉ around 83.3 μm. This band has been observed at low resolutionJ. W. Fleming, Infrared Phys. 18, 791 (1978); K. V. Chance and W. A. Traub, J. Mol. Spectrosc. 95, 306 (1982).ut without precise determination of the band center. More recently, the analysis of the mid-IR ν₈ and ν₈ + ν₉ band spectral regions of ³⁵ClONO₂ allowed the indirect but accurate determination of the ν₉ band centerJ.-M. Flaud, W. J. Lafferty, J. Orphal, M. Birk, and G. Wagner, Mol. Phys. 101, 1527 (2003). In this work, the 83.3 μm region of ClONO₂ has been recorded at high resolution (0.001 cm⁻¹) using a Fourier transform spectrometer and the SOLEIL synchrotron light source. The spectrum corresponds to the absorption of the torsional mode, ν₉ around 123 cm⁻¹and a series of nν₉-(n-1)ν₉ hot bands. In this talk, the analysis of the ν₉ bands of ³⁵ClONO₂ and ³⁷ClONO₂ and 2ν₉-ν₉ band of ³⁵ClONO₂ will be presented. In turn, this will enable an analysis of the hot bands involving low energy levels in the mid-IR region where ClONO₂ is detected and modelled.

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Footnotes:

P. J. Crutzen, Quart. J. Royal Met. Soc. 96, 320 (1970); M. J. Molina and F. S. Rowland, Nature 249, 810 (1974).. D. G. Murcray et al., Geophys. Res. Lett. 6, 857 (1979)., H. Fischer et al., Atmos. Chem. Phys. 8, 2151 (2008).a R. Zander et al., Geophys. Res. Lett. 13, 757 (1986).. J. Orphal, M. Birk, G. Wagner, and J.-M. Flaud, Chem. Phys. Lett. 690, 82 (2017).. J. W. Fleming, Infrared Phys. 18, 791 (1978); K. V. Chance and W. A. Traub, J. Mol. Spectrosc. 95, 306 (1982).b J.-M. Flaud, W. J. Lafferty, J. Orphal, M. Birk, and G. Wagner, Mol. Phys. 101, 1527 (2003)..

Nitryl chloride (ClNO₂) is of atmospheric interest, since it is produced by heterogeneous reactions, in the marine troposphere, between NaCl sea-salt aerosols and gaseous N₂O₅B. J. Finlayson-Pitts et al., Nature 337, 241 (1989); W. Behnke et al., J. Aerosol Sci. 24, 115 (1993); H. D. Osthoff et al., Nat. Geosci. 1, 324 (2008). in the polluted continental airL. H. Mielke et al., Environ. Sci. Technol. 45, 8889 (2011); G. J. Phillips et al., Geophys. Res. Lett. 39, L10811 (2012). and possibly also on polar stratospheric clouds, between N₂O₅ and solid HClM. A. Tolbert, M. J. Rossi, and D. M. Golden, Science 240, 1018 (1988); M. T. Leu, Geophys. Res. Lett. 15, 851 (1988). Many high-resolution spectroscopic studies of ClNO₂ in the microwave and mid-infrared regions are availableJ.-M. Flaud, A. Anantharajah, F. Kwabia Tchana et al., JQSRT 224, 217 (2019). However, ClNO₂ presents two fundamentals in the far-infrared region below 600 cm⁻¹, with the lowest one corresponding to the Cl-N stretching mode, ν₃ around 370 cm⁻¹. A new investigation of the ν₃ bands of ³⁵ClNO₂ and ³⁷ClNO₂ has been performed using a high resolution (0.00102 cm⁻¹) Fourier transform spectrum recorded at SOLEIL with highly improved experimental conditions as compared to a previous studyJ. Orphal, M. Morillon-Chapey, S. Klee, G. C. Mellau, and M. Winnewisser, J. Mol. Spectrosc. 109, 101 (1998). leading to a well resolved spectrum. As a consequence, significantly better results than previously were obtained. The line assignments were pursued up to higher J and K_a quantum number values, J = 83 and K_a = 44. For both isotopomers, a total of 6331 transitions were reproduced with a root-mean-square deviation of 2×10⁻⁴ cm⁻¹using a Watson-type A-reduced Hamiltonian. Improved band centers, rotational and centrifugal distortion constants for the ν₃ fundamental bands of ³⁵ClNO₂ and ³⁷ClNO₂ have been determined. The synthetic line list obtained in this study will be interesting for future measurements of ClNO₂ in the atmosphere, e.g. using the new satellite mission FORUM (ESA) covering the 150-1400 cm⁻¹spectral region.

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Footnotes:

B. J. Finlayson-Pitts et al., Nature 337, 241 (1989); W. Behnke et al., J. Aerosol Sci. 24, 115 (1993); H. D. Osthoff et al., Nat. Geosci. 1, 324 (2008)., L. H. Mielke et al., Environ. Sci. Technol. 45, 8889 (2011); G. J. Phillips et al., Geophys. Res. Lett. 39, L10811 (2012)., M. A. Tolbert, M. J. Rossi, and D. M. Golden, Science 240, 1018 (1988); M. T. Leu, Geophys. Res. Lett. 15, 851 (1988).. J.-M. Flaud, A. Anantharajah, F. Kwabia Tchana et al., JQSRT 224, 217 (2019).. J. Orphal, M. Morillon-Chapey, S. Klee, G. C. Mellau, and M. Winnewisser, J. Mol. Spectrosc. 109, 101 (1998).,

Recent observations of a possible SH absorption feature in the atmosphere of a hot Jupiter exoplanet have sparked a renewed interest in the molecule's electronic spectroscopy, motivating the creation of a new line list.Gorman et al., Mon. Not. R. Astron. Soc. 490, 1652 (2019)his list currently relies on absolute transition frequencies measured nearly 70 years ago with a grating spectrograph.Ramsay, J. Chem. Phys. 20, 1920 (1952)hile the 0.03 cm⁻¹ accuracy achieved in these experiments was impressive for the time, measurements using modern laser spectroscopy techniques can do much better. In this talk, I will present our measurements of the A ²Σ⁺,v′=0 ← X ²Π_3/2,v"=0,J"=3/2 transitions in SH using a continuous-wave ultraviolet laser stabilized to an optical frequency comb. The same apparatus was previously used to measure A−X transitions in OHFast et al. Phys. Rev. A 98, 052511 (2018) Due to the broader linewidths and lower fluorescence detection efficiency caused by a short A state predissociation lifetime, the SH transition frequencies could not be determined as precisely as those in OH. We were nevertheless able to determine the frequencies of 12 transitions from the rotational ground state with an absolute uncertainty of less than 1.2 MHz (4×10⁻⁵ cm⁻¹).

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Footnotes:

Gorman et al., Mon. Not. R. Astron. Soc. 490, 1652 (2019)T Ramsay, J. Chem. Phys. 20, 1920 (1952)W Fast et al. Phys. Rev. A 98, 052511 (2018).

We observed rotationally resolved spectra of A(0⁺) ← X(0⁺) and B(1) ← X(0⁺) transition of PbO produced in a flow cell by laser ablation. The transition frequency was calibrated using an ultralow expansion etalon and (4s ²S_1/2 - 5p ²P_1/2) absorption line of K atoms at 405 nm within the error of 3 MHz. We determined the rotational constants for a number of vibrational levels of three isotopic molecules, ²⁰⁶PbO, ²⁰⁷PbO, and ²⁰⁸PbO. The interaction among electronic excited states are generally significant in such heavy molecules, and we found perturbations in specific rotational levels [1]. We discuss the potential energy curves of low electronic excited states of PbO on the basis of the global analysis of observed transitions.
[1] K. Enomoto, A. Fuwa, N. Hizawa, Y. Moriwaki, and K. Kobayashi, J. Mol. Spectrosc., 339, 12 (2017)

r0pt Figure Trioxane, (H₂CO)₃, is a symmetric top that belongs to the C_3v symmetry group. The molecule owns 20 fundamental modes that are dispatched as 7 symmetric vibrations of type A1, 3 vibrations of type A2 and 10 doubly degenerate vibrations of type E. Infrared spectra of trioxane have been recorded in the 50-650 cm⁻¹ range using a high resolution Bruker IFS 125 interferometer located at the AILES beamline of the SOLEIL synchrotron facility. Owing to its higher brilliance in the far-infrared region, the SOLEIL synchrotron radiation was used to improve the signal-to-noise ratio of the spectrum at the maximal resolution of 0.001 cm⁻¹. We present here a detailed analysis and modeling of intense OCO deformation ν₇ and ν₁₉ modes as well as weaker CH₂ torsion ν₂₀ mode and its first overtone 2ν₂₀. Thanks to the formalism and programs developed in Dijon, we could determine accurately the effective Hamiltonian parameters for these 3 modes.

The (1,0) vibrational band of the [13.10] Ω=1 – X ³Σ⁻(0⁺) transition of tungsten sulfide (WS) has been measured in absorption using Intracavity Laser Spectroscopy with Fourier transform detection (ILS-FTS). WS was synthesized in a 0.05-0.15 A DC current plasma discharge within a tungsten lined hollow cathode at 625 mTorr with 65% Ar, 17.5% He, 17.5% H₂, and a trace amount of CS₂. The spectrum was calibrated using literature values for argon lines and PGOPHER’s calibration feature [C.M. Western, J. Quant. Spectrosc. Radiat. Transfer 2016 (186), 221-242]. Three rotational branches (P , Q-, and R-branch) with four WS isotopologues (¹⁸²WS, ¹⁸³WS, ¹⁸⁴WS, and ¹⁸⁶WS) were observed in the spectrum. Molecular constants for these isotopologues were determined for both electronic states. The line positions of the (0,0) band of this transition [L.F. Tsang et al., J. Mol. Spectrosc. 2019 (359), 31-36] were included in the fit. The results of the analysis will be presented, and compared with calculations [L.F. Tsang et al., 2019].