The application of multi-reference pump-probe simulation method to XUV signatures of ultrafast alkyl halides photodissociation

UV pump-XUV probe measurements have been successfully applied in the study of photo-induced chemical reactions. Although rich element-specific electronic structure information is accessible within XUV (inner-shell) absorption spectra, it can be difficult to interpret the chemistry directly from the spectrum. Due to the multi-reference character of the excited states of heavier alkyl halide molecules, we developed and applied a multi-reference method to completely simulate UV pump-XUV probe measurements to study photodissociation in alkyl halides molecules. Fewest switches surface hopping (FSSH) trajectories were used to explore the coupled electronic and ionic dynamics upon photoexcitation. Interpretation of previous measurements is provided by associated multi-reference, restricted active space, inner-shell spectral simulations. This combination of FSSH trajectories and XUV spectra provides an interpretation of experimental transient features and validates the branching ratio between different spin-orbit split states in the photodissociated products. This methodology should prove useful for interpretation of the increasing number of inner-shell probe studies of molecular excited states or for designing new experiments to control the direction of chemical reactions.