Concerning the Optical Absorption Band of the Hydrated Electron

Abstract

AbstractPhotobleaching of hydrated electrons in liquid water has been attempted under the immense light flux of a Q‐switched ruby laser. The 20 nanosecond ruby pulse was utilized as both the exciting light and a monitor for the absorbance of eaq−. Whereas stable solutions of organic dyes (cryptocyanine and methylene blue) showed marked nonlinear absorption due to saturation of optical transitions, no such change was observed for hydrated electrons even though the light intensity was varied by >107 up to 200 photons per hydrated electron per cm2. Consequently the photoexcited state lifetime is estimated to be less than 6 · 10−12 sec. This finding is discussed briefly in terms of three possible origins for the absorption band, namely that involving excitation to a bound excited state, as a photoionization efficiency profile or as a distribution of potential wells of various depths.