A time-dependent wave packet analysis of the dynamics of transition state spectroscopy in one dimension

The transition state absorption spectrum and the dynamics of the excited state are calculated for a one-dimensional reactive system with the basic features of the reaction K+NaCl→KCl+Na. We have propagated a Gaussian minimum wave packet on two Eckart potential curves coupled by an intense laser field, where the bound states supported by the upper potential well are exactly solved. By applying time-dependent perturbation theory, the continuum–bound transitions are calculated, and a bound excited state is obtained when the wave packet reaches the interactive region. The transition probabilities show a strong dependence on laser frequency which is well explained by Franck–Condon calculations. By contrast, a Landau–Zener model is quantitatively incorrect. By studying the excited wave packet dynamics and the transition probability spectra at different times, we conclude that the excitation to the upper potential surface is not localized to crossings of the dressed potential curves.