Polarization degrees of 3p 2P3/2–3s 2S1/2 transition in O5+(1s 23p) produced in collisions of O6+ with He and H2

Abstract

Electron capture processes in collisions of O6+ with ground state He and H2 are investigated using the two-centre atomic orbital close-coupling method. Total and state-selective one-electron capture cross sections are obtained for collision energies between 0.5 and 300 keV/u. The comparison with the available experimental state-selective capture data in the overlapping energy range (0.5–100 keV/u for O6++He and 0.5–8 keV/u for O6++H2) shows a good overall agreement. The polarization degrees of 3p 2P3/2–3s 2S1/2 radiation from O5+(3p 2P3/2) produced in O6++He and O6++H2 collisions are calculated from the magnetic substate-selective cross sections with inclusion of cascade contributions from higher n = 4 and n = 5 states. Good agreement is obtained with the experimental data available in the energy range 3–8 keV/u. Below ∼10 keV/u, the polarization degrees of O5+(3p 2P3/2) in both collision systems exhibit an oscillatory structure and above this energy they steadily increase with the increase of collision energy, reaching the values of about 0.37 at 300 keV/u. The energy behaviour of the polarization degree of O5+(3p 2P3/2) in the O6++He collision system is determined almost exclusively by the direct electron capture to 3p0 and 3p1 states of O5+, while in the case of the O6++H2 collision system in the energy region below ∼40 keV/u it is strongly affected by the cascade contributions from the 4l states, which are the dominant capture states in this system.