Using time-resolved photoelectron spectroscopy to unravel the electronic relaxation dynamics of photoexcited molecules.

Time-resolved photoelectron spectroscopy measurements combined with quantum chemistry and dynamics calculations allow unprecedented insight into the electronic relaxation mechanisms of photoexcited molecules in the gas-phase. In this Tutorial Review, we explain the essential concepts linking photoelectron spectroscopy measurements with electronic structure and how key features on the potential energy landscape are identified using quantum chemistry and quantum dynamics calculations. We illustrate how time-resolved photoelectron spectroscopy and theory work together using examples ranging in complexity from the prototypical organic molecule benzene to a pyrrole dimer bound by a weak N-Hπ interaction and the green fluorescent protein chromophore.