Spin-orbit effects in the Penning ionization: Ar + He∗ (23S) → Ar+(2P3/2,2P1/2) + He + e−. An ab initio and trajectory study

Spin-orbit effects in the Penning ionization have been investigated theoretically. Ab initio calculations with the Feshbach projection operator have been carried out to obtain the potential energy curves and the partial widths for each spin-orbit ionized state. Quasiclassical trajectory calculations have been performed based on these quantities, and the dependence of the ionization cross sections on collisional energy has been evaluated in the range 0.05–1 eV. The calculations show that the ratio of the cross section for the 2P3/2 ionized state to that for te 2P1/2 state increases with collisional energy, in agreement with experimental results.