Study of the IH+Br dynamics using a Born—Oppenheimer separation between light and heavy nucleus motions

Abstract

The study of the dynamics of heavy—light + heavy systems using the Born—Oppenheimer-type separation between the light and the heavy nuclear motions is presently extended to the IH+Br system. The hydrogenic wavefunctions that describe the H nucleus motion for clamped I and Br nuclei, and the potential energy curves that govern the I—Br relative motion are reported. Particular attention has been paid to the hydrogenic state for which the potential energy curve has a well. Surprisingly, it is found that this state does not participate in the H-atom exchange process in the reactive collision: IH ( v=0, j) + Br → I+HBr( v′, j′). This reaction mainly proceeds via crossings between diabatic potential energy curves correlated to the IH ( v=0, j) + Br and I + HBr( v′=1, v′=2, j′) limits. In addition, the photodetachment spectrum of the IHBr − anion has been calculated. The present 3D result fairly agrees with the recent calculation of Metz and Neumark (J. Chem. Phys. 97 (1992) 962). Salient features of the photodetachment spectrum stem from the hydrogenic wavefunctions properties.