Excess Electron States in Dense Polar Vapors

Abstract

We report the results of a theoretical study of the energy levels and the optical properties of excess electrons in water and ammonia polar vapors. A molecular model for short range interactions and continuum model for long range interactions were adopted. Variational self-consistent solutions were obtained for the ground and for the first-excited states. We have calculated the density dependence of the configurational diagrams, the equilibrium ground state radius, the heat of solution, the vertical excitation energy, the temperature coefficient of the absorption maximum and the optical line width. The localized excess electron is stable in ammonia and in water vapors down to the lowest calculated density of 0.1 g cm−3, while the transition energy exhibits a weak density dependence in this region. To assess the stability of the localized excess electron at low densities we have handled electron binding by a “supermolecule” consisting of a cluster of N = 4 solvent molecules, where in the case of NH3 the localized electron state is unstable while for H2O it is on the verge of stability. New experimental data are reported in the absorption spectrum of the localized excess electron in subcritical and supercritical D2O in the density range 0.5–0.15 g cm−3. The results of the theoretical calculations compare favorably with the available experimental data.