Beyond Decay Times: Probing Nonadiabatic Molecular Dynamics

Nonadiabatic processes play an important role in photophysics and photochemistry involved in chemistry, materials, and biology. A focus of our work is to develop our understanding of excited state processes and nonadiabatic events in molecular systems. We achieve this by a closely collaborative approach between theory and experiment, where we calculate time resolved observables, such as photoelectron spectra, ultrafast electron diffraction or kinetic energy release signals, and compare to the corresponding experimental pump-probe signals. Recently, we have focused on examining how different pump or probe energies affect the dynamics or the signals. In nitrophenol we have shown that excitation at different wavelengths leads to different pathways in the dynamics, even though excited state decay times appear very similar. This is a cautionary story that we cannot rely on decay time constants alone to study the dynamics, and a better approach is to use a combination of experimental techniques and theory for interpretation. Other systems we have investigated with various theoretical and experimental probe techniques will be discussed as well.