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1. Localized and delocalized bound states of the main isotopologue 48 O 3 and of 18 O-enriched 50 O 3 isotopomers of the ozone molecule near the dissociation threshold

   https://doi.org/10.1039/D0CP02177F  

   Kokoouline, Viatcheslav ; Lapierre, David ; Alijah, Alexander ; Tyuterev, Vladimir ( January 2020 , Physical Chemistry Chemical Physics)

   Knowledge of highly excited rovibrational states of ozone isotopologues is of key importance for modelling the dynamics of exchange reactions, for understanding longstanding problems related to isotopic anomalies of the ozone formation, and for analyses of extra-sensitive laser spectral experiments currently in progress. This work is devoted to new theoretical study of high-energy states for the main isotopologue 48 O 3 = 16 O 16 O 16 O and for the family of 18 O-enriched isotopomers 50 O 3 = { 16 O 16 O 18 O, 16 O 18 O 16 O, 18 O 16 O 16 O} of the ozone molecule considered using a full-symmetry approach. Energies and wave functions of bound states near the dissociation threshold are computed in hyperspherical coordinates accounting for the permutation symmetry of three identical nuclei in 48 O 3 and of two identical nuclei in 50 O 3 , using the most accurate potential energy surface available now. The obtained vibrational band centers agree with observed ones with the root-mean-squares deviation of about 1 cm −1 , making the results appropriate for assignments and analyses of future experimental spectra. The levels delocalized between the three potential wells of ozone isomers are computed and analyzed. The states situated deep in the three (for 48 O 3 ) or two (for 50 O 3 ) equivalent potential wells have similar energies with negligible splitting. However, the states situated just below the potential barriers separating the wells, are split due to the tunneling between the wells resulting in the splitting of rovibrational sub-bands. We evaluate the amplitudes of the corresponding effects and consider possible perturbations in vibration–rotation bands due to interactions between three potential wells. Theoretical predictions for the splitting of observable band centers are provided for the first time. 

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2. Far-Infrared Synchrotron Spectroscopy of a Potentially Important Interstellar Isotopologue of Vinyl Alcohol: CH 2 CHOD

   https://doi.org/10.1021/acs.jpca.9b11514  

   Bunn, Hayley ; Hull, Killian ; Miller, Isaac ; Raston, Paul L. ( October 2019 , The Journal of Physical Chemistry A)

   null (Ed.)
3. Isotopologue trace gas detection using multipass cavity Raman scattering

   https://doi.org/10.1364/CLEO_AT.2022.AM2M.3  

   Singh, Jaspreet ; Muller, Andreas ( May 2022 , Conference on Lasers and Electro-Optics: Applications and Technology 2022)

   Feedback-assisted multipass-cavity spontaneous Raman scattering is demonstrated as an effective method of isotopologue analysis. Deuterium concentration precision near one part-per-million in water was obtained by direct vapor and indirect dihydrogen measurements.

    

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4. Multi-isotopologue laser absorption spectroscopy of carbon monoxide for high-temperature chemical kinetic studies of fuel mixtures

   https://doi.org/10.1016/j.combustflame.2019.05.030  

   Pineda, Daniel I. ; Bendana, Fabio A. ; Schwarm, Kevin K. ; Spearrin, R. Mitchell ( September 2019 , Combustion and Flame)
5. Wide-field CO isotopologue emission and the CO-to-H 2 factor across the nearby spiral galaxy M101

   https://doi.org/10.1051/0004-6361/202245718  

   den Brok, Jakob S. ; Bigiel, Frank ; Chastenet, Jérémy ; Sandstrom, Karin ; Leroy, Adam ; Usero, Antonio ; Schinnerer, Eva ; Rosolowsky, Erik W. ; Koch, Eric W. ; Chiang, I-Da ; et al ( August 2023 , Astronomy & Astrophysics)

   Carbon monoxide (CO) emission constitutes the most widely used tracer of the bulk molecular gas in the interstellar medium (ISM) in extragalactic studies. The CO-to-H 2 conversion factor, α 12 CO(1−0) , links the observed CO emission to the total molecular gas mass. However, no single prescription perfectly describes the variation of α 12 CO(1−0) across all environments within and across galaxies as a function of metallicity, molecular gas opacity, line excitation, and other factors. Using spectral line observations of CO and its isotopologues mapped across a nearby galaxy, we can constrain the molecular gas conditions and link them to a variation in α 12 CO(1−0) . Here, we present new, wide-field (10 × 10 arcmin 2 ) IRAM 30-m telescope 1 mm and 3 mm line observations of 12 CO, 13 CO, and C 18 O across the nearby, grand-design, spiral galaxy M101. From the CO isotopologue line ratio analysis alone, we find that selective nucleosynthesis and changes in the opacity are the main drivers of the variation in the line emission across the galaxy. In a further analysis step, we estimated α 12 CO(1−0) using different approaches, including (i) via the dust mass surface density derived from far-IR emission as an independent tracer of the total gas surface density and (ii) local thermal equilibrium (LTE) based measurements using the optically thin 13 CO(1–0) intensity. We find an average value of ⟨ α 12 CO(1 − 0) ⟩ = 4.4  ±  0.9  M ⊙  pc −2  (K km s −1 ) −1 across the disk of the galaxy, with a decrease by a factor of 10 toward the 2 kpc central region. In contrast, we find LTE-based α 12 CO(1−0) values are lower by a factor of 2–3 across the disk relative to the dust-based result. Accounting for α 12 CO(1−0) variations, we found significantly reduced molecular gas depletion time by a factor 10 in the galaxy’s center. In conclusion, our result suggests implications for commonly derived scaling relations, such as an underestimation of the slope of the Kennicutt Schmidt law, if α 12 CO(1−0) variations are not accounted for. 

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