Collisional Excitation and Non-LTE Modeling of Interstellar Chiral Propylene Oxide

Karlis Dzenis (1, 2) , A Faure (1) , B. A. Mcguire (3, 4) , A. J. Remijan (4) , P. J. Dagdigian (5) , C. Rist (1) , R. Dawes (6) , E. Quintas-Sanchez (6) , François Lique (7) , M. Hochlaf (8)

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
2 Edin. - University of Edinburgh
3 MIT - Massachusetts Institute of Technology
4 NRAO - National Radio Astronomy Observatory [Charlottesville]
5 JHU - Johns Hopkins University
6 Missouri S&T - Missouri University of Science and Technology
7 IPR - Institut de Physique de Rennes
8 COSYS - Département Composants et Systèmes

The first set of theoretical rotational cross sections for propylene oxide (CH3CHCH2O) colliding with cold He atoms has been obtained at the full quantum level using a high-accuracy potential energy surface. By scaling the collision reduced mass, rotational rate coefficients for collisions with para-H-2 are deduced in the temperature range 5-30 K. These collisional coefficients are combined with radiative data in a non-LTE radiative transfer model in order to reproduce observations of propylene oxide made toward the Sagittarius B2(N) molecular cloud with the Green Bank and Parkes radio telescopes. The three detected absorption lines are found to probe the cold (similar to 10 K) and translucent (n (H) similar to 2000 cm(-3)) gas in the outer edges of the extended Sgr B2(N) envelope. The derived column density for propylene oxide is N (tot) similar to 3 x 10(12) cm(-2), corresponding to a fractional abundance relative to total hydrogen of similar to 2.5 x 10(-11). The present results are expected to help our understanding of the chemistry of propylene oxide, including a potential enantiomeric excess, in the cold interstellar medium.

Domains: Physics [physics]

Karlis Dzenis, A Faure, B. A. Mcguire, A. J. Remijan, P. J. Dagdigian, et al.. Collisional Excitation and Non-LTE Modeling of Interstellar Chiral Propylene Oxide. The Astrophysical Journal, 2022, 926 (1), pp.3. ⟨10.3847/1538-4357/ac43b5⟩. ⟨hal-03592648v1⟩