A XMS-CASPT2 Non-Adiabatic Dynamics Study on Pyrrole

The photoinduced dynamics of pyrrole is revisited employing the independent trajectory surface hopping methodology based on extended multi-state second order perturbation theory (XMS-CASPT2). Excitation at 200 nm into a high density of states region gives rise to ultrafast deactivation via internal conversion. The primary dissociation channel was found to be N-H hydrogen abstraction, resulting in pyrrolyl radical formation. The associated time constant for hydrogen dissociation was determined to be 64 +/- 13 fs, in good agreement with the experimental value of 52 +/- 12 fs (Roberts et al., 2013). A total kinetic energy spectrum was also computed, that is in qualitative agreement with experiment. Radiationless decay via the ring-puckering crossing seam was identified as a minor deactivation channel.