Femtosecond midinfrared spectroscopy of water (heavy water) after two photo
n excitation at 9 eV provides clear evidence for two short-lived precursors
of the hydrated electron preceding the well-known "wet electron." The meas
ured first intermediate with peak absorption at 2.9 (4.1) mu m is proposed
to represent an O(H,D):e(-) complex. The subsequent solvation proceeds via
e(-):[(H,D)(2)O](n) complexes at approximately 1.6 (2.0) mu m in the electr
onic ground state, involving an increasing number of water molecules during
the first 200 fs and followed by the wet electron.