INFRARED-LASER KINETIC SPECTROSCOPY OF THE H-3+ ION

Diode laser kinetic spectroscopy was employed to investigate the dissociative recombination of H-3+ (upsilon = 0) in the afterglow of a hollow cathode discharge through H-2. The concentrations of H-3+ as well as of electrons were measured as a function of time and the latter was found to be higher in the afterglow and decay More slowly. The major ions present were determined by mass analysis to be H-3+, H+, H2O+ and H3O+. Higher-order ambipolar diffusion modes were found to contribute slightly to the total diffusion process (almost-equal-to 20% in the time range 20-140 mus), as determined from the measured radial electron density distribution. Although the electron density was explicitly included in the kinetic equations and the presence of water was accounted for, no precise value for the recombination rate constant could be derived, except that the rate of 2 X 10(-7) cm3 s-1, previously measured by infrared spectroscopy, has to be considered as an upper limit.