A GUIDED-ION BEAM STUDY OF THE HYDROGEN-ATOM TRANSFER-REACTION OF STATE-SELECTED N-2(+) WITH H-2 AT COLLISION ENERGIES RANGING FROM SUBTHERMAL TO 2-EV (CM)

This article presents detailed internal and kinetic energy dependent cross sections and reaction rates for the hydrogen atom transfer processes N 2+(X 2Σg+, v + = 0-4, J+ = 2)+H2→N2H + + H, which were obtained under single-collision conditions in a guided-ion beam/scattering gas experiment. Preparation of ions in specific states relied on single-color excitation within a resonantly enhanced (2+1) multiphoton ionization scheme. The translational energy of the ions, E lab, was varied from 0.1 eV to approximately 30 eV. A small activation barrier impedes the reaction. Vibronic state preparation of the nitrogen ion is influential on the nature of the energy surface - N 2++H2 or H2++N 2 - along which the H atom transfer proceeds. Calculations of model potential energy surfaces suggest that the reaction pathway must involve several exoergic and endoergic channels which open successively as the collision energy increases. A purely collision determined cross section-as would be evidenced by the E-1/2 dependence formulated in the Langevin-Gioumousis-Stevenson model - is observed only within a narrow window of kinetic energies. © 1995 American Institute of Physics.