Investigation on the photofragmentation of hydrogen chloride

The photofragmentation of HCl molecules from the first absorption band has been studied. The extinction coefficients were obtained from numerical calculations, while the radial non-adiabatic transition probabilities for the excitation from the A1Π1 to the t3Σ1+ electronic state are predicted by resorting to the Rosen-Zener-Demkov (RZD) model. The wavelength-dependent branching fraction is determined and agrees generally with experiment. The RZD coupling model is used to examine the contribution of the radial nonadiabatic transition, which causes the branching of the products. The results suggest that the foremost source of the redistribution of quantum flux is caused by radial derivative coupling, which occurs between the initially populated A state and the triplet t state. Furthermore, the interference effect is more apparent near the long-wavelength tail region of the A1Π1 ← X absorption profile.