Revisiting the pump-probe polarized transient hole-burning of the hydrated electron: Is its absorption spectrum inhomogeneously broadened?

Although simulations have predicted that the hydrated electron's absorption spectrum is inhomogeneously broadened, the experiments in the Literature that test this prediction have produced contradictory results. In this Letter, we describe new polarized transient hole-burning experiments on solvated electrons in both water and methanol. Although we chose excitation wavelengths that should have maximized any polarization dependence in the bleaching dynamics, we were unable to observe any anisotropy. We conclude that the absorption spectrum of the hydrated electron is more homogeneously broadened than suggested by the simulations, although the extent to which the band is inhomogeneously broadened remains an open question. (C) 2004 Elsevier B.V. All rights reserved.