This article deals with the direct probing of water cages that assist two well-defined prehydration electron transfers (PHETs) with the reactive metal cation Cd2+. Early electron photodetachment processes are triggered by a two-photon UV excitation of aqueous halide ion Cl- (R = [H2O]/[CdCl2] = 110). Concomitant with an ultrafast Cd2+ reduction by IR p-like excited electron (J. Phys. Chem. A 1998, 102, 7795), a subpicosecond oxidoreduction reaction occurs in caged three-body complexes {Cl..e(-)..Cd2+}(aq). Near-IR spectroscopic measurements give a PHET frequency of 1.38 +/- 0.02 10(12) s(-1). This reduction reaction is 70 times faster than a diffusion-controlled bimolecular reaction between aqueous Cd2+ ions and fully hydrated electrons (s-state). Femtosecond spectroscopic data indicate that preexisting bridging water-molecule-bonded Cl-...Cd2+ pairs (SSIP-like configurations) assist efficient prehydration electron transfer. Because the 4s-like orbital radius of nascent {Cl..e(-)..Cd2+}(aq) configurations is larger than the mean distance of Cd2+-Cl- ion pairs in a first coordination sphere of Cd2+ ions (similar to2.6 Angstrom), it is suggested that an overlap between a 4s electron orbital and the localized Cd2+ orbital favors an early inner-sphere electron transfer. For the first time, a nonlinear relationship is defined between the rate of Cd2+ univalent reduction and the energy level of the trapped electron (IR e(p)(-), {Cl..e(-)..Cd2+}(aq), e(aq)(-)). We conclude that the short-time water cagings govern the course of PHET events and influence early branchings between elementary oxidoreduction reactions in ionic environments.