Electron-impact excitation of neutral oxygen

Abstract

Aims. Our goal was to calculate transition rates from ground and excited states in neutral oxygen atoms due to electron collisions for non-LTE modelling of oxygen in late-type stellar atmospheres, thus enabling the reliable interpretation of oxygen lines in stellar spectra. Methods. A 38-state R-matrix calculation in LS -coupling has been performed. Basis orbitals from the literature are adopted, and a large set of configurations are included to obtain good representations of the target wave functions. Rate coefficients are calculated by averaging over a Maxwellian velocity distribution. Results. Estimates for the cross sections and rate coefficients are presented for transitions between the seven lowest LS states of neutral oxygen. The cross sections for excitation from the ground state compare well with existing experimental and recent theoretical results. © ESO 2007.