Binary and ternary recombination of and ions with electrons in low temperature plasma

Abstract

Measurements of recombination rate coefficients of binary and ternary recombination of and ions with electrons in a low temperature plasma are described. The experiments were carried out in the afterglow plasma in helium with a small admixture of Ar and parent gas (H2 or D2). For both ions a linear increase of measured apparent binary recombination rate coefficients (αeff) with increasing helium density was observed: αeff = αBIN + K He[He]. From the measured dependencies, we have obtained for both ions the binary (αBIN) and the ternary (K He) rate coefficients and their temperature dependence. For the description of observed ternary recombination a mechanism with two subsequent rate determining steps is proposed. In the first step, in + e− (or + e−) collision, a rotationally excited long-lived Rydberg molecule (or ) is formed. In the following step (or ) collides with a He atom of the buffer gas and this collision prevents autoionization of (or ). Lifetimes of the formed (or ) and corresponding ternary recombination rate coefficients have been calculated. The theoretical and measured binary and ternary recombination rate coefficients obtained for and ions are in good agreement.