Spectroscopy and dynamics of van der Waals reactions: the Ba⋯FCH3∗ photofragmentation channels

The simultaneous measurement of both the photodepletion action spectrum of the Ba⋯FCH3 complex and the action spectra of the reactive BaF and non-reactive Ba photofragmentation channels, over the energy range 17795–18250 cm−1 allowed direct determination of the reaction probabilities of a van der Waals reaction as a function of excitation energy. The energy dependence of the Ba⋯FCH3+hν→(Ba⋯FCH3)∗→BaF∗+CH3 and Ba∗+CH3 reaction probabilities showed an oscillatory behaviour with opposite phase, which could be due to quantal interferences between the two photofragmentation channels. In addition the energy spacing of the oscillations can be related to the internal motions of the transition state.