Experimental study of the dynamics of D+H2 reactive and inelastic collisions below 1.0 eV relative energy

We report the results of state-to-state dynamics experiments on the D+H2→HD+H reaction as well as D+H2→H°2+D energy transfer at relative energies of 0.67 and 0.79 eV. Both product state distributions and absolute partial cross sections have been determined, from coherent anti-Stokes Raman scattering (CARS) spectra of the HD and H°2 products recorded under single-collision conditions following pulsed-laser photolysis of DI to generate the D atom reactant. At both energies and for both reactive and inelastic collisions there is a strong dynamical bias against rotational and vibrational excitation of the product. However, at 0.67 eV there is an enhancement of both the relative and absolute yield of HD (v′=1), and to a lesser extent H2(v′=1), the only energetically accessible vibrationally excited product states. This may be the result of a Feshbach resonance at ≈0.65 eV, just above the v′=1 threshold energy. Product quantum state distributions from quasiclassical trajectory calculations are in fairly good agreement with the experimental results, except that they do not show the v′=1 enhancement at 0.67 eV. However, the partial cross sections from the trajectory calculations are systematically larger than those measured.