Novel Precursors of Solvated Electrons in Water: Evidence for a Charge Transfer Process

Femtosecond midinfrared spectroscopy of water (heavy water) after two photon excitation at 9 eV provides clear evidence for two short-lived precursors of the hydrated electron preceding the well-known “wet electron.” The measured first intermediate with peak absorption at 2.9 $(4.1)\mu \mathrm{m}$ is proposed to represent an $\mathrm{O}(\mathrm{H},\mathrm{D}):e^{-}$ complex. The subsequent solvation proceeds via $e^{-}:\left[\right(\mathrm{H},\mathrm{D}{)}_2\mathrm{O}{]}_n$ complexes at approximately 1.6 $(2.0)\mu \mathrm{m}$ in the electronic ground state, involving an increasing number of water molecules during the first 200 fs and followed by the wet electron.