Reactive collision dynamics of Na*(4 2P)+H2 and HD: Experiment and theory

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Abstract
We have used a ‘‘half‐collision’’ pump–probe technique to measure the far wing absorption profiles of the NaH2 collision complex leading to the nonreactive formation of Na* and to four distinct final rotational states of the reaction product NaH(v‘=1, J‘=3, 4, 11, and 13). We have observed reaction on both the attractive potential energy surfaces and over a barrier on the repulsive surface. We have observed the effect of the Na* reagent electronic orbital alignment on the NaH final product rotational state distribution. Specifically, absorption to the repulsive surface leads preferentially to low‐rotational product states, while absorption to the attractive surfaces leads preferentially to high‐rotational product states of NaH. Isotopic substitution experiments give evidence of a kinematic isotope effect on the product rotational state distribution for reactive trajectories on the repulsive surface. We have developed a simple model using a quantum mechanical line shape calculation to estimate the NaH2 absorption probability as a function of wavelength. We then make simple phenomenological dynamical arguments to predict final state branching. There is an overall qualitative agreement between the experimental results and theoretical model predictions.