QUANTAL STATE-TO-STATE H-ATOM EXCHANGE CROSS-SECTIONS OF LOW-ENERGY IH(UPSILON=0)+BR REACTIONS

The dynamics of the IH + Br heavy-light + heavy system is treated usin g the Born-Oppenheimer-type separation between the light and the heavy nuclear motions. The hydrogenic wavefunctions, that describe the H-nu cleus motion for clamped I and Br nuclei, provide the potential energy curves and couplings that govern the I-Br relative motion. The H-atom exchange cross sections in the reactive collision: IH(upsilon = 0;j) + Br --> I + HBr(upsilon',j') are found to strongly depend upon j and to be large only for upsilon' = 1 with j' = 16-20 and for upsilon' = 2 with j' = 8-11. The present results are compared to our previous esti mates, to results of classical trajectory calculations and to availabl e experimental data.