Electron solvation dynamics in water and methanol studied by femtosecond spectroscopy in the mid-infrared

This paper determines the relaxation dynamics of the already generated, long-lived solvated electrons in water, in a probing range in the mid-infrared spectra. Interesting details of the readjustment of the solvation layer are observed after excitation of the electrons by a 820 nm pulse (duration 80 fs) to the first excited level (a localized 2p-state). In addition, this novel probe absorption data in the range 2 - 5 μm reveal a strong, but short-lived coupling of the electron to the OH- (OD-) stretching vibration of the solvent molecules. Our data suggest that an observed 240 fs relaxation time represents internal conversion to an intermediate state, interpreted as a ground state electron in a hot environment, similar to the "wet electron" observed in the photoionisation process.