TIME-DEPENDENT CALCULATION OF REACTIVE FLUX EMPLOYING COMPLEX ABSORBING POTENTIALS - GENERAL-ASPECTS AND APPLICATION WITHIN THE MULTICONFIGURATION TIME-DEPENDENT HARTREE WAVE APPROACH

A novel modification of the flux operator formalism is introduced that combines the merits of the flux operator approach with those of compl ex absorbing potentials. The method is used to determine initial-state selected reaction probabilities for a broad energy range from a singl e appropriately chosen time-dependent wave packet. The propagation may be performed solely in the coordinates of the reagents arrangement ch annel. State-to-state transition probabilities can also be obtained wh en appropriate projectors are included. In contrast to similar methods the present one does not require the calculation of derivatives with respect to the reaction coordinate. More importantly, it avoids the ne ed to (E,t)-Fourier transform the wave packet at every grid point on a dividing surface. The proposed formula, though completely general, is especially well suited to handle multiconfiguration time-dependent Ha rtree wave functions. As a check of the reliability initial-state sele cted reaction probabilities for the collinear H+H-2-->H-2+H reaction a re calculated and compared with (numerically) exact results. We also s how that the initial wave packet may be placed close to the interactio n region when its energy distribution is corrected for the mean potent ial energy. (C) 1996 American Institute of Physics.