Electron-ion recombination in low temperature hydrogen/deuterium plasma

Abstract

The stationary afterglow with cavity ring down spectrometer (SA-CRDS) was used to study the recombination of H3 + , H2 D+ , 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 + , H2 D+ , 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 .