Lithium [Li*(2 2P J)] fine structure transitions and quenching induced by collisions with molecular hydrogen [H2, D2

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Dye laser excitation and interferometric fluorescence analysis techniques were used to measure collision induced quenching and fine structure transition rate coefficients in the 7Li*(2 2PJ)+H2,D2 systems at a temperature of 564 K. The quenching and fine structure transition energy transfer processes all occur at ’’gas kinetic’’ rates, but the magnitudes of cross sections for each process are determined by different electronically nonadiabatic interactions at different ranges of internuclear separation. Fine structure transition cross sections are determined by the forms of long range interaction potentials, which are undoubtedly very similar to those of the isoelectronic Li*(2 2PJ)+He system. Quenching cross sections are determined by short-to-intermediate range interaction potentials, some of which may effectively be coupled by fine structure transitions. Simple dynamical models provide limited insight into these rate processes, suggesting that ab initio potential hypersurface calculations plus refined quantal and/or semiclassical dynamical computations using these hypersurfaces are required for proper treatment of the Li*(2 2PJ)+ H2,D2 systems.