Excitation of the Spin Multiplets of the Ground State of Oxygen by Slow Electrons

Abstract

Electron excitation cross sections of the transitions between the three spin multiplets $J=0,1,2\mathrm{}$, of the ${\left[{\mathrm{}\left(1s\right)\mathrm{}}^2{\mathrm{}\left(2s\right)\mathrm{}}^2{\mathrm{}\left(2p\right)\mathrm{}}^4\right]}^{3}P$ ground state of the neutral oxygen atom have been calculated by using the continuous-state Hartree-Fock formulation for electron energies of 500-10 000°K. Partial-wave analysis is performed in a coupled representation characteristic of the total angular momentum of the entire system. The scattering equations are further simplified by neglecting the coupling between the different partial waves of the incident electron. Under an exact-resonance approximation, the scattering equations for the $s$ wave can be completely decoupled and the solutions obtained by numerical iteration. The $p$-wave manifold consists of three sets of simultaneous equations. Exact solutions (close-coupling) are obtained for selected scattering equations and are compared with the corresponding collision strengths calculated by a modified distorted-wave treatment to examine the validity of the latter approximate method. Final collision strengths for the $p$ wave are evaluated from appropriate combinations of the close-coupling and weak-coupling schemes. Partial cross sections for the $d$ wave are found to be of minor importance and may be obtained with the Born approximation. Corrections for the energy differences between atomic states are found to be small. The calculated cross sections are somewhat larger than the values estimated by Gershberg and provide evidence for the importance of the role of neutral oxygen atoms in the cooling of the interstellar media.