A full-dimensional wave packet dynamics study of the photodetachment spectra of FCH4(-)

The low-resolution photodetachment spectrum of FCH(4)(-) is studied in full dimensionality employing the multi-configurational time-dependent Hartree approach and potential energy surfaces recently developed by Bowman and co-workers. The computed spectrum qualitatively agrees with the low-resolution spectrum measured by Neumark and co-workers. It displays two peaks which can be assigned to different vibrational states of methane in the quasi-bound F·CH(4) van der Waals complex. The first intense peak correlates to methane in its vibrational ground state while the second much smaller peak results from methane where one of the bending modes is excited. The present simulations consider only a single potential energy surface for the neutral FCH(4) system and thus do not include spectral contributions arising from transitions to excited electronic states correlating to the F((2)P) + CH(4) asymptote. Considering the quantitative differences between the computed and the experimental spectra, one cannot decide whether beside the vibrational excitation of the methane fragment also electronic excitation of FCH(4) contributes to the second peak in the experimental photodetachment spectrum.