Hot atom reaction yields in Mu(*)+H-2 and T-*+H-2 from quasiclassical trajectory cross sections on the Liu-Siegbahn-Truhlar-Horowitz surface

In order to provide an assessment of the "global" accuracy of the Liu-Siegbahn-Truhlar-Horowitz (LSTH) potential surface for H-3, hot atom reaction yields, which are determined from collision processes over an energy range much wider than that of single-collision experiments, have been calculated for the Mu*+H-2 and T*+H-2 systems. The isotopic comparison of muonium (Mu=mu(+)e(-)), an ultralight isotope of hydrogen (m(Mu)/m(H)approximate to 1/9), with the heaviest H-atom isotope, tritium, is a novel approach in testing the global accuracy of the H-3 surface. These reaction yields have been calculated using a formalism developed for (mu(+)) charge exchange, with input cross sections for elastic, inelastic (rovibrational excitation) and reactive collisions determined from quasi classical trajectories on the LSTH surface, in the center-of-mass energy range 0.5-11 eV. The rate of energy loss of the hot atom (Mu* or T*) due to elastic and inelastic collisions with the moderator (H-2) drastically affects the hot atom reaction yield. In particular, the forwardness of the angular differential cross section for the elastic process plays a crucial role in determining the stopping power for hot atoms. Good agreement is obtained in the absolute yields for both Mu(*)+H-2 and T-*+H-2, for the first time from microscopic cross sections, demonstrating that the LSTH surface remains surprisingly accurate over a wide range of energy and isotopic mass. (C) 2000 American Institute of Physics. [S0021- 9606(00)01920-6].