BORN-OPPENHEIMER TYPE SEPARATION IN THE STUDY OF THE DYNAMICS - APPLICATION TO PHOTODETACHMENT OF CLHCL- AND CLDCL-

The Born-Oppenheimer type separation between light and heavy nuclear m otions is applied to the study of the dynamics of the ClHCl and ClDCl systems. Approximate and elaborate approaches are used to calculate th e photodetachment spectra of the ClHCl- and ClDCl- anions. The approxi mate approach is based on a Born-Oppenheimer approximation where the n uclear wave function of the ClHCl or ClDCl systems is obtained as a si ngle product of two wave functions which describe the motion of the li ght H(D) nucleus for clamped chlorine nuclei and the motion of the hea vy chlorine nuclei, respectively. The elaborate approach is a multista te description which goes beyond the Born-Oppenheimer approximation. T he relevant close coupling equations are solved numerically subject to proper photodissociation asymptotic conditions. The results obtained in this approach confirm the validity of the approximate one and provi de additional information on the ClH + Cl and ClD + Cl decay channels. Resonances are obtained at energies of 0.640 eV and 0.899 eV for the ClHCl system, and at 0.538 eV and 0.715 eV for the ClDCl system. They are identified as shape or Feshbach resonances and analyzed in terms o f the normal modes of a linear symmetrical triatomic molecule. (C) 199 6 American Institute of Physics.