THE H+PARA-H2 REACTION - INFLUENCE OF DYNAMIC RESONANCES ON H-2 (V'=1,J'=1 AND 3) INTEGRAL CROSS-SECTIONS

We have measured integral rate constants for the reaction H + para-H-2 --> H-2(nu' = 1, j' = 1 and 3) + H at 11 center-of-mass collision energies (E(rel)) between 0.88 and 1.01 eV, a region in which dynamical scattering resonances are present. We have also measured the H-2(nu' = 1, j' = 3)/H-2(nu' = 1, j' = 1) population ratio at two additional values of E(rel) outside of this range. Tunable uv laser photolysis of HI was used to generate translationally hot H atoms of variable kinetic energy. Quantum-state-specific detection of the H-2 reaction product was accomplished via (2 + 1) resonance-enhanced multiphoton ionization and time-of-flight mass spectrometry. The integral rate constants have a smooth dependence on E(rel), in agreement with the recent quantum-mechanical (QM) calculations of Zhang and Miller and contrary to the experimental results of Nieh and Valentini. The QM results are in nearly perfect agreement with the present measurements for the dependence on E(rel) of both the integral rate constants and the H-2(nu' = 1, j' = 3)/H-2(nu' = 1, j' = 1) population ratio. It is concluded that measurements of integral cross sections as a function of collision energy are not highly sensitive to the presence of dynamical resonances in this system.