Chapter 43 - The solvated electron in methanol. Novel time- and frequency-resolved pump-probe spectroscopy of short-lived precursors

Abstract

In spectroscopic studies, the solvated electron is often used as a microscopic probe for the structural dynamics, since the solvent molecules strongly influence the electron properties. These interactions manifest in a change of the optical absorption, which is governed by the transition from an s-like ground state to a p-like excited state of the electron in its interaction potential with the solvation shell. Using ultrashort laser pulses, the generation process of the solvated electrons could be studied in various liquids, e.g. water and alcohols. With typical lifetimes of the solvated electron in the order of 10-9s, the trapped charges were further studied by pump-probe-spectroscopy monitoring the relaxation process following (re-)excitation of the already formed species. This chapter shows a combined investigation of both the generation process of solvated electrons and of pump-probe-spectroscopy of intermediate states including the final equilibrated ground state. As shown previously, the formation of the solvated electron in methanol takes place within ∼10 ps. About an order of magnitude slower than in water, the timescale of this process allows to investigate the precursor states in much more detail using a state-of-the-art laser system.