Quantum Calculation of Inelastic CO Collisions with H: I. rotational quenching of low-lying rotational levels

TL;DR

This paper presents new quantum scattering calculations for CO rotational deexcitation by H collisions, providing updated rate coefficients across a wide temperature range, with implications for astrophysical observations.

Contribution

It introduces novel quantum scattering calculations using two different potential energy surfaces, highlighting differences from previous models and assessing uncertainties.

Findings

Rate coefficients vary significantly at low temperatures due to PES differences.

Current results align with expected propensity rules.

Discrepancies with earlier calculations emphasize the importance of PES choice.

Abstract

New quantum scattering calculations for rotational deexcitation transitions of CO induced by H collisions using two CO-H potential energy surfaces (PESs) from Shepler et al. (2007) are reported. State-to-state rate coefficients are computed for temperatures ranging from 1 to 3000 K for CO($v=0,j$) deexcitation from $j=1-5$ to all lower $j^\prime$ levels, with $j$ being the rotational quantum number. Different resonance structures in the cross sections are attributed to the differences in the anisotropy and the long-range van der Waals well depths of the two PESs. These differences affect rate coefficients at low temperatures and give an indication of the uncertainty of the results. Significant discrepancies are found between the current rate coefficients and previous results computed using earlier potentials, while the current results satisfy expected propensity rules. Astrophysical applications to modeling far infrared and submillimeter observations are briefly discussed.