  Monomers and small clusters of such molecules can reversibly trap conduction
band electrons in dilute alkane solutions. The dynamics and energetics of this
trapping have been studied using pulse radiolysis - transient absorption
spectroscopy and time-resolved photoconductivity. Binding energies, thermal
detrapping rates, and absorption spectra of excess electrons attached to
monomer and multimer solute traps are obtained and possible structures for
these species are discussed. "Dipole coagulation" (stepwise growth of the
solute cluster around the cavity electron) predicted by Mozumder in 1972 is
observed. Acetonitrile monomer is shown to solvate the electron by its methyl
group, just like the alkane solvent does. The electron is dipole-bound to the
CN group; the latter points away from the cavity. The resulting negatively
charged species has a binding energy of 0.4 eV and absorbs in the infrared.
Molecules of straight-chain aliphatic alcohols solvate the excess electron by
their OH groups; at equilibrium, the predominant electron trap is a trimer or a
tetramer; the binding energy of this solute trap is ca. 0.8 eV. Trapping by
smaller clusters is opposed by the entropy which drives the equilibrium towards
the electron in a solvent trap. For alcohol monomers, the trapping does not
occur; a slow proton transfer reaction occurs instead. For acetonitrile
monomer, the trapping is favored energetically but the thermal detachment is
rapid (ca. 1 ns).
