Binary and ternary recombination of H2D+ and HD2+ ions with electrons at 80 K

Abstract

The recombination of deuterated trihydrogen cations with electrons has been studied in afterglow plasmas containing mixtures of helium, argon, hydrogen and deuterium. By monitoring the fractional abundances of H₃⁺, H₂D⁺, HD₂⁺ and D₃⁺ as a function of the [D₂]/[H₂] ratio using infrared absorption observed in a cavity ring down absorption spectrometer (CRDS), it was possible to deduce effective recombination rate coefficients for H₂D⁺ and HD₂⁺ ions at a temperature of 80 K. From pressure dependences of the measured effective recombination rate coefficients the binary and the ternary recombination rate coefficients for both ions have been determined. The inferred binary and ternary recombination rate coefficients are: α_binH2D(80 K) = (7.1 ± 4.2) × 10⁻⁸ cm³ s⁻¹, α_binHD2(80 K) = (8.7 ± 2.5) × 10⁻⁸ cm³ s⁻¹, K_H2D(80 K) = (1.1 ± 0.6) × 10⁻²⁵ cm⁶ s⁻¹ and K_HD2(80 K) = (1.5 ± 0.4) × 10⁻²⁵ cm⁶ s⁻¹.