Accurately probing the electronic structure and dynamics of molecules excited above S<sub>1</sub> presents significant challenges for both theory and experiment. In particular, strong interactions among multiple excited states cause rapid relaxation from the higher-lying excited states to S<sub>1</sub>, as described by Kasha more than 50 years ago. Theoretical methods promise to offer the best insight on rapid non-adiabatic relaxation, but require experimental benchmarks for comparison and validation. Toward this end, we present an experimental perspective on the electronic structure and dynamics of several compounds that photoisomerize. We use both one- and two-photon excitation techniques to access different initially excited states, as well as new regions of the higher-lying excited states that are not accessible via direct excitation of the lowest optically accessible excited state. As expected, the electronic lifetimes of higher-lying excited states are very short (typically ~100 fs or less), but nevertheless lead to different reaction pathways in some cases. The measurements provide insight on the role of non-adiabatic electronic relaxation, as well as a surprisingly weak influence of excess vibrational energy, in the excited-state reaction dynamics.

Experimental perspective on the electronic structure and dynamics of higher-lying electronic states

249th National Meeting (2015)

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