A quantum-mechanical investigation of O(3P) + CO scattering cross sections at superthermal collision energies
Authors: Khalil Malathe , Chhabra Sanchit , Gacesa Marko , Al Ghaferi Amal , El-Kork Nayla 
Published: February 2023

The Martian atmospheric gas loss may have played a role in transforming Mars from a warmer, water-containing planet into a cold and dry one. This loss is attributed to different phenomena, including photodissociation of H2O followed by Jeans escape and photochemical escape of hot O atoms.&#160; It was proposed that collisions with hot (super-thermal) neutral atoms can eject light species from the atmosphere such as He [1], D[2], H2 [3], and OH[4]. Here, collisions with super-thermal oxygen atoms are the most important because of its kinetic energy and abundance. Carbon monoxide (CO) has been used as a probe for studying the planet&#8217;s atmospheric composition and the dynamics involved [5]. In this study, we computed the elastic and inelastic integral and differential cross-sections for CO collisions with energetic O(3P) and its isotopes using a full coupled-channel quantum mechanical formalism at collision energies from 0.4 to 5 eV. The O+CO interactions were described using recently constructed potential energy surfaces of 3A&#8242;, 3A&#8243;, and 23A&#8243; symmetry [6], dissociating to the atomic ground state. The state-to-state, elastic, and inelastic cross-sections were calculated for individual surfaces as well as their statistical average [7]. We applied the new cross sections in a simple 1D column transport model to provide revised escape and energy transfer rates of O(3P) and its isotopes in thermal CO gas, at the conditions corresponding to the upper atmosphere of Mars, where CO is abundant.References:[1]&#160;&#160;&#160;&#160;&#160;&#160; S. Bovino, P. Zhang, F. A. Gianturco, A. Dalgarno, and V. Kharchenko, &#8220;Energy transfer in O collisions with He isotopes and Helium escape from Mars,&#8221; Geophys. Res. Lett., vol. 38, no. 2, pp. 2&#8211;6, 2011, doi: 10.1029/2010GL045763.[2]&#160;&#160;&#160;&#160;&#160;&#160; P. Zhang, V. Kharchenko, M. J. Jamieson, and A. Dalgarno, &#8220;Energy relaxation in collisions of hydrogen and deuterium with oxygen atoms,&#8221; J. Geophys. Res. Sp. Phys., vol. 114, no. 7, pp. 1&#8211;14, 2009, doi: 10.1029/2009JA014055.[3]&#160;&#160;&#160;&#160;&#160;&#160; M. Gacesa, P. Zhang, and V. Kharchenko, &#8220;Non-thermal escape of molecular hydrogen from Mars,&#8221; Geophys. Res. Lett., vol. 39, no. 10, pp. 1&#8211;6, 2012, doi: 10.1029/2012GL050904.[4]&#160;&#160;&#160;&#160;&#160;&#160; M. Gacesa, N. Lewkow, and V. Kharchenko, &#8220;Non-thermal production and escape of OH from the upper atmosphere of Mars,&#8221; Icarus, vol. 284, pp. 90&#8211;96, 2017, doi: 10.1016/j.icarus.2016.10.030.[5]&#160;&#160;&#160;&#160;&#160;&#160; M. Zhang and D. Shi, &#8220;Transition properties of the X 1 &#931; + , I 1 &#931; &#8722; , A 1 &#928; , D 1 &#916; , B 1 &#931; + , and a 3 &#928; states of carbon monoxide,&#8221; Comput. Theor. Chem., vol. 1202, no. May, p. 113302, 2021, doi: 10.1016/j.comptc.2021.113302.[6]&#160;&#160;&#160;&#160;&#160;&#160; R. L. Ja, G. M. Chaban, and M. Field, &#8220;Collisional Dissociation of CO&#8239;: ab initio Potential Energy Surfaces and Quasiclassical Trajectory Rate Coe cients,&#8221; pp. 1&#8211;54, 2019.[7]&#160;&#160;&#160;&#160;&#160;&#160; S. Chhabra, M. Gacesa, M. S. Khalil, A. Al Ghaferi, and N. El-kork, &#8220;A quantum-mechanical investigation of O(3P) + CO scattering cross sections at superthermal collision energies,&#8221; Mon. Not. R. Astron. Soc., no. October, 2022, doi: https://doi.org/10.1093/mnras/stac3057.&#160;