Stability Criterion for the Localization of an Excess Electron in a Nonpolar Fluid

In this paper we consider the properties of an excess electron in the nonpolar dense fluids 3He, 4He, Ne, Ar, and H2. The energy of the quasifree electron state was estimated through the use of an approximate polarization potential and of pseudopotential theory, together with average Wigner–Seitz boundary conditions. The Wigner–Seitz approximation was also applied to the study of the localized state. A stability criterion was derived for the localization of an excess electron in a dense fluid of nonpolar molecules. The stability criterion is expressed in terms of a relation between the energy of the quasifree electron state and the bubble surface energy. Three cases of physical interest which can be distinguished are those of the existence of a quasifree state, the existence of a metastable bubble, and the formation of an energetically stable bubble. The stability criterion predicts that excess electron states in liquid He and in liquid He, should be localized, the excess electron state in liquid Ar should be quasifree, while liquid neon provides a borderline case between the stable and the metastable bubble. The available experimental data concerning the energy barrier for adiabatic electron injection and electron mobilities in liquid He, liquid H2, and liquid Ar are consistent with the results of the present treatment.