Using a low-temperature 22-pole ion trap apparatus, detailed measurements for the title reaction have been performed between 10?K and 100?K in order to get some state specific information about this fundamental hydrogen abstraction process. The relative population of the two lowest H2 rotational states, j?= 0 and 1, has been varied systematically. NH+ formation is nearly thermo-neutral; however, to date, the energetics are not known with the accuracy required for low-temperature astrochemistry. Additional complications arise from the fact that, so far, there is no reliable theoretical or experimental information on how the reactivity of the N+ ion depends on its fine-structure (FS) state 3 Pja . Since in the present trapping experiment, thermalization of the initially hot FS population competes with hydrogen abstraction, the evaluation of the decay of N+ ions over long storage times and at various He and H2 gas densities provides information on these processes. First assuming strict adiabatic behavior, a set of state specific rate coefficients is derived from the measured thermal rate coefficients. In addition, by recording the disappearance of the N+ ions over several orders of magnitude, information on nonadiabatic transitions is extracted including FS-changing collisions.
展开▼
