Collisional excitation of water by hydrogen atoms

TL;DR

This paper presents quantum dynamical calculations of water's rotational excitation due to collisions with hydrogen atoms, providing new rate coefficients across a wide temperature range using a high-accuracy potential energy surface.

Contribution

First quantum dynamical calculations of H$_2$O excitation by H atoms using a high-accuracy potential energy surface and close-coupling formalism, covering extensive energy levels and temperatures.

Findings

New collisional rate coefficients for H$_2$O / H collisions

No simple relation between H$_2$O / H and other collisional systems

Specific calculations are necessary for different collisional partners

Abstract

We present quantum dynamical calculations that describe the rotational excitation of H$_2$O due to collisions with H atoms. We used a recent, high accuracy potential energy surface, and solved the collisional dynamics with the close-coupling formalism, for total energies up to 12 000 cm$^{-1}$. From these calculations, we obtained collisional rate coefficients for the first 45 energy levels of both ortho- and para-H$_2$O and for temperatures in the range T = 5-1500 K. These rate coefficients are subsequently compared to the values previously published for the H$_2$O / He and H$_2$O / H$_2$ collisional systems. It is shown that no simple relation exists between the three systems and that specific calculations are thus mandatory.