Optical potential discrete variable representation method in the adiabaticrepresentation - Application to the CO(B-1 Sigma(+)-D '(1)Sigma(+), J=0) predissociation process

The optical potential discrete variable representation method (OP-DVR) has been applied recently to calculate resonances in the framework of the diaba tic representation [J. Chem. Phys. 101, 7580 (1994)]. This method is based on the conjoint use of the discrete variable representation (DVR) method an d the properties of a complex absorbing potential (CAP). The OP-DVR method is the DVR version of the CAP stabilization method initially proposed by Jo licard and Austin [Chem. Phys. Lett. 121, 106 (1985)]. In the present study , we show that this efficient and accurate method can also be applied withi n the adiabatic representation since it allows one to overcome in a simple way, numerical difficulties associated with the first derivative operator w hich appears in the expression of non adiabatic couplings. Within the OP-DV R method, the choice of the representation (diabatic or adiabatic) is gover ned by physical arguments and by the fact that the potentials and the coupl ings are known in one or the other of these two representations. In the cas e where the potentials and the couplings are obtained in the adiabatic repr esentation, we show in this paper that the transformation into the diabatic framework is not necessary. We demonstrate that the discrete variable repr esentation can be a simple and an efficient way to deal with the adiabatic representation.