The dynamics of the hydrogen exchange reaction at 2.20 eV collision energy: Comparison of experimental and theoretical differential cross sections

The H + D-2 (upsilon = 0, j = 0) --> HD(upsilon', j') + D isotopic variant of the hydrogen atom exchange reaction has been studied in a crossed molecu lar beam experiment at a collision energy of 2.20 eV. Kinetic energy spectr a of the nascent D atoms were obtained by using the Rydberg atom time-of-fl ight technique. The extensive set of spectra collected has permitted the de rivation of rovibrationally state-resolved differential cross sections in t he center-of-mass frame for most of the internal states of the HD product m olecules, allowing a direct comparison with theoretical predictions. Accura te 3D quantum mechanical calculations have been carried out on the refined version of the latest Boothroyd-Keogh-Martin-Peterson potential energy surf ace, yielding an excellent agreement with the experimentally determined dif ferential cross sections. The comparison of the results from quasi-classica l trajectory calculations on the same potential surface reveals some discre pancies with the measured data, but shows a good global accordance. The the oretical calculations demonstrate that, at this energy, reactive encounters are predominantly noncollinear and that collinear collisions lead mostly t o nonreactive recrossing. The experimental results are satisfactorily accou nted for by theoretical calculations without consideration of Geometric Pha se effects. (C) 1999 American Institute of Physics. [S0021-9606(99)01420-8] .