Negative ions in cryogenic media (Review Article)

Abstract

We discuss localization of free electrons embedded in cryogenic media. These electrons do not bind to gas atoms within the confinement length of the order of the Bohr radius, but can participate in formation of “condensons”—many-particle complexes first introduced and studied by Lifshitz. The formalism is based on the construction of the interaction energy, W(a0, ng), between the electron and the gas medium. The functional form of W(a0, ng) is generally non-linear in the gas density ng and the details of the interaction between the electron and a single atom in the gas approximation are determined from the characteristic scattering length a0, which determines both the sign and strength of W(a0, ng). An explicit expression for W(a0, ng), allows for a uniform description of various effects based on formation of “condensons” of electronic origin observed in cryogenic media. These include formation of bubbles (“bubble effect”) for a0 > 0 and possibly alternative, charged gas density enhancement domains for a0...