Theoretical study of the electron-induced vibrational excitation of H2O

Abstract

This study presents calculations for cross sections of the vibrational excitation of H2O(X1A1) via electron impact. The theoretical approach employed here is based on first principles only, combining electron-scattering calculations performed using the UK R-matrix codes for several geometries of the target molecule, three-dimensional (3D) vibrational states of H2O, and 3D vibrational frame transformation. The aim is to represent the scattering matrix for the electron incident of the molecule. The vibrational wave functions were obtained numerically, without the normal-mode approximation, so that the interactions and transitions between vibrational states assigned to different normal modes could be accounted for. The thermally averaged rate coefficients were derived from the calculated cross sections for temperatures in the 10–10 000 K interval and analytical fits for rate coefficients were also provided. We assessed the uncertainty estimations of the obtained data for subsequent applications of the rate coefficients in modelling the non-local thermal equilibrium (non-LTE) spectra of water in various astrophysical environments.