CAPTURE CROSS-SECTIONS ON ADIABATIC VIBRONIC POTENTIAL CURVES - THE REACTION OF AR+(2PJ)+H2

Capture cross sections and rate constants have been calculated for collisions of state-selected Ar+ (2P(J)) ions with H2 (v = 0). The calculations were done using the orientation-averaged adiabatic vibronic (AV) potential energy curves for this system. After correcting for the fact that half of all Ar+ (2P3/2) + H2 collisions are completely unreactive, the capture cross sections are assumed to equal the reactive cross sections for the process Ar+ (2P(J)) + H2 (v = 0) --> ArH+ + H. The calculations agree well with the experimental data for this system at collision energies below 0.5 eV. In particular, the increase in the rate constant with collision energy is shown to be due to the strongly attractive nature of the potential curves at small distances.