Singlet-triplet excitation spectrum of the CO-He complex.: II.: Photodissociation and bound-free CO(a 3Π←X1Σ+) transitions

The dissociating states of the triplet-excited CO-He complex are studied by means of scattering calculations on ab initio diabatic potential energy surfaces produced in the preceding paper (Paper I). With the aid of an effective transition dipole function and the bound states of the CO-He complex in the ground singlet state we obtain the photoabsorption cross section as a function of the excitation energy and generate the full UV spectrum of the singlet-triplet transition. It was found that the dominant contributions to the spectrum, in the energy range from - 5 to + 10 cm(-1) relative to the band origin at 48 473.201 cm(-1), originate from resonances that correspond to higher spin-orbit levels of the excited CO(a 3(Pi)) - He complex with approximate quantum number \Omega\ = 1. Rapid predissociation, with the triplet CO fragment decaying into its lower spin-orbit levels with Omega = 0, limits the lifetime of these excited levels to, typically, 10-700 ps. We also predict the rotational and spin-orbit state distribution of the triplet CO fragment and the maximum deflection angle of the photodissociation products in a molecular beam experiment. (C) 2003 American Institute of Physics.