The dynamics of the reaction D+2+O(3P) →OD++D, and the influence of the atomic quadrupole moment on the cross section at very low kinetic energies

Abstract

We report the results of a merged-beam study of the reaction D+2+O(3P) →OD++D over the range of relative kinetic energy from 0.002 to 27 eV. The data include accurate absolute values of the total reaction cross section and also high-resolution measurements of the product ion laboratory energy distributions, which are deconvoluted to obtain estimates of the product energy and angle distributions in c.m. coordinates. The reaction mechanism is direct, with the OD+ product scattered preferentially in the direction of the incident O atom, and with large average internal excitation. The fact that O(3P) possesses an electrostatic quadrupole moment has important consequences for the interpretation of the low-energy data in terms of the adiabatic state correlations of reactants, intermediates, and products. Our major conclusions are (1) that the average probabilities of reaction for low-energy capture collisions are about 87% for approaches on Σ−–A2 potential energy surfaces and about 53% for approaches on Π–B1, B2 surfaces and (2) that the data are not consistent with the assumption of electronic adiabaticity.