Abstract
Stationary afterglow measurements in conjunction with near-infrared absorption spectroscopy show that the recombination of the H-3(+) ion with electrons in ionized gas mixtures of He, Ar, and H-2 at 300 K is strongly enhanced by neutral helium and by molecular hydrogen. The H-2-assisted ternary recombination coefficient K-H2 = (8.7 +/- 1.5) x 10(-23) cm(6)s(-1) substantially exceeds the value measured for H-3(+) in ambient helium (K-He similar to 10(-25) cm(6) s(-1)) or predicted by the generally accepted classical theory of Bates and Khare (similar to 10(-27) cm(6) s(-1)) for atomic ions.
Because of the extremely large value of K-H2 in a hydrogen plasma the ternary recombination dominates over binary recombination already at pressures above 3 Pa. This can have consequences in plasma physics, astrophysics, recombination pumped lasers, plasma spectroscopy, plasmatic technologies, etc.
The ternary processes provide a plausible explanation for the discrepancies between many earlier experimental results on H-3(+) recombination. The observation that the ternary process saturates at high He and H-2 densities suggests that recombination proceeds by a two-step process: formation of a long-lived complex [with a rate coefficient alpha(F) = (1.5 +/- 0.1) x 10(-7) cm(3) s(-1)] followed by collisional stabilization.