The emission and emission excitation spectra of various hydroxides, acids and halide salts, separately and in combination, have been measured in aqueous, methanolic and ethanolic solutions. The shifts of spectra as a function of solvent, the disappearance of emission in ethanol and the enhancement of the emissivity of the acids by the addition of halide salts suggest that the emitting entity is an exciplex of the hydrogen atom with water. The candidacy of(H 3O .) ★ or, better [(H 2O) n H .] ★ as the emitter accords with all experimental information; however, GAUSSIAN 80 calculations for the lowest-energy quartet state suggest that this state is dissociative in the gas phase.