Inelastic collisions of n=3 helium atoms with normal helium atoms: associative ionisation

Abstract

Helium atoms are excited to an n=3 level by pulsed laser light in a glow discharge plasma, and the subsequent temporal development of the upper-level populations and the electron density are determined from the emission line intensities and by the microwave cavity resonance method, respectively. Associative ionisation rate coefficients are obtained for 31P-, 31D- and 33D-state atoms. When combined with the previous determination of the excitation transfer and total depopulation collision rate coefficients a consistent set of rate coefficients is obtained. A qualitative discussion on the detailed mechanism of these transitions is given on the basis of the diabetic molecular potential curve crossings.