Nonadiabatic Electronic Dynamics in Isolated Molecules and in Solution Studied by Ultrafast Time–Energy Mapping of Photoelectron Distributions

Abstract

Abstract Nonadiabatic electronic dynamics contribute to the diversity of chemical reactions. We investigate nonadiabatic dynamics in isolated molecules and aqueous solutions by time-resolved photoelectron spectroscopy. For isolated molecules in the gas phase, we combine two-dimensional imaging detection of electrons and a sub-20 fs deep UV and vacuum UV light source to measure time-evolution of the photoelectron kinetic energy and angular distributions. Time–energy mapping of photoelectron angular anisotropy reveals the S2 → S1 internal conversion dynamics through conical intersection in pyrazine, benzene, and toluene. The time–energy mapping is also employed to extract the photoelectron angular distribution in the molecular frame for nitric oxide. For electronic dynamics in aqueous solution, we employ time-resolved photoelectron spectroscopy using a liquid beam and an electrostatic or a time-of-flight electron energy analyzer. Successful observation of ultrafast electron-transfer reactions in aqueous solutions and measurement of electron binding energies of solvated species suggest promising future developments of this very young field.