The hydrated electron has been studied by mixed quantum/classical (MQC) simulations in the past decades, but there is still controversy concerning its structure. Most pseudopotentials used in such simulations give a cavity structure, where the electron interrupts the water H-bonding by carving out a void to reside in. Recently, based on a new pseudopotential, we proposed a different picture where the wavefunction of the hydrated electron significantly overlaps the water. In this work, we explore the temperature dependence of the excited-state relaxation of these cavity and non-cavity models of the hydrated electron. We use non-adiabatic MQC dynamics, along with ultrafast spectroscopic measurements, to determine the excited-state lifetime as a function of temperature. Our simulations predict that the non-cavity electron has a lifetime that changes by a factor of ~2 between 0 and 50 °C, whereas the cavity electron shows at most a 10% change in lifetime over this same temperature range. This difference in behavior leads to very different predictions for stimulated emission from the excited electron. Our ultrafast experiments clearly show stimulated emission behavior similar and a temperature-dependent lifetime similar to that predicted by the non-cavity model, suggesting that the cavity model misses important physics for this system.

Temperature dependence of the hydrated electron’s excited-state relaxation: Distinguishing cavity and non-cavity models

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.