Regular Article

Electron-ion recombination in low temperature hydrogen/deuterium plasma^★

¹ Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, 18000 Prague, Czech Republic
² Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, 12116 Prague, Czech Republic

^* e-mail: juraj.glosik@mff.cuni.cz

Received: 28 June 2017
Received in final form: 16 October 2017
Accepted: 21 November 2017
Published online: 30 January 2018

Abstract

The stationary afterglow with cavity ring down spectrometer (SA-CRDS) was used to study the recombination of H₃⁺, H₂D⁺, HD₂⁺ and D₃⁺ ions with electrons in low temperature (77–300 K) plasmas in He/Ar/H₂/D₂ gas mixtures. By measuring effective recombination rate coefficients (α_eff) in plasma with mixtures of ions and their dependences on temperature and partial densities of He, H₂ and D₂, α_eff (T, [He],[H₂],[D₂]), we determined binary (α_binH3, α_binH2D, α_binHD2, α_binD3) and ternary (K_H3, K_H2D, K_HD2, K_D3) recombination rate coefficients for H₃⁺, H₂D⁺, HD₂⁺ and D₃⁺ ions. For all four ions we observed very efficient He assisted ternary recombination which is comparable with binary recombination already at [He] =1 × 10¹⁷ cm⁻³. The removal of excited particles in afterglow plasma was monitored to obtain the plasma thermalisation rate at given experimental conditions. The inferred deexcitation rates for reaction of helium metastable atoms with D₂ are k_D2 (300 K)=(2.1 ± 0.3) × 10⁻¹⁰ cm³ s⁻¹ and k_D2 (140 K)=(1.3 ± 0.3) × 10⁻¹⁰ cm³ s⁻¹.