Monitoring the removal of excited particles in He/Ar/H-2 low temperature afterglow plasma at 80-300 K
Abstrakt
Stationary afterglow (SA) experiments with cavity ring down absorption spectrometer (cw-CRDS) have been used to study recombination of H-3(+) ions with electrons. To characterize the plasma during the afterglow we monitored the time evolution of density of He-2 excited dimers (a(3)Sigma(+)(u)) in plasmas in pure helium and in helium with small admixture of Ar and H-2.
By monitoring the plasma decay and its dependence on [H2] and [Ar] in the afterglow in pure He and in He/Ar/H-2 mixture we estimated the rate of plasma thermalization in the temperature range of 80-300 K. The inferred deexcitation rate coefficients for reaction of helium metastable atoms with H-2 were (0.9 x 0.3) x10(-10) cm(3) s(-1), (1.9 x 0.2) x10(-10) cm(3) s(-1) and (2.7 x 0.2) x 10(-10) cm(3) s(-1) at 80 K, 140 K and 300 K, respectively.
The effective recombination rate coefficients for H-3(+) were evaluated from the decay of the electron number density. We propose the lower estimate for the saturation of the effective recombination rate coefficient in H-3(+) and D-3(+) dominated plasma.