Reactions of H* (22P-22S) + H2 and their isotopes

The four possible H- and D-substituted reactions in the title have been studied at room temperature using an optically thin flow system. An experimental cross section for total collisional deactivation in each reaction has been measured by analyzing the quenching of Lyman-α fluorescence; the results cover a range of 84–91 Å2, with an individual uncertainty of 5%. An experimental cross section for associative ionization has also been measured for each reaction using ion collection techniques; these results cover a range of 0.82–1.10 Å2±5%. For the reactants H*(n=2)+D2, the experimental cross section for producing D*(n=2)+HD is 0.28 Å2±25%. It has been measured by analyzing H and D Lyman-α fluorescence signals which are observed simultaneously. The product channels observed and the other exothermic channels (for example HDvib+D, and H+D+D) are discussed in terms of intersections of qualitative potential energy surfaces, and it is suggested that nearly all quenching produces three ground state atoms. Collisional interconversion of the 22P and 22S states of H*(n=2) and D*(n=2) is also discussed. Because of this process, each of the experimental results is related to a pair of reactions-one involving the 22P state and the other the 22S state.