Abstract
We have obtained the binary and the ternary electron-ion recombination rate coefficients and their temperature dependence for H3+ and D3+ ions (produced in the mixture He/Ar/parent-gas H2 or D2) in the afterglow plasma. A mechanism with two subsequent rate-determining steps is proposed to explain the observed ternary recombination rate.
In the first step, in $H_3^+ + e$ (or $D_3^+ + e$) collision, a rotationally excited long-lived Rydberg molecule H3* (or D3*) is formed. In the following step this collides with a He atom of the buffer gas and this collision prevents the autoionization of H3* (or D3*).
Lifetimes of H3* (or D3*) and corresponding ternary recombination rate coefficients have been calculated. The theoretical and measured binary and ternary recombination rate coefficients obtained for H3+ and D3+ ions are in good agreement.