Absorption coefficient of H⁻ and interparticle interaction-I. Debye-Hückel approximation

Abstract

The absorption coefficient of H⁻ in presence of interparticle interaction has been determined under the Debye-Hückel approximation. The effect of perturbers, both on the number density and on the photodetachment cross section, has been considered. The presence of perturbers alters the ground state wave function of H⁻ negligibly but reduces the binding energy of H⁻ by an amount directly proportional to α = 1/γ_D where γ_D is the Debye-length for α ≪ 1. The relative changes in the binding energy, in number density, as well as in the photodetachment cross section due to the interparticle interaction are almost independent of the ground-state wave function used in either the length, velocity or acceleration formalism. For α ≠ 0, i.e. in presence of perturbers, the number density of H⁻ per hydrogen atom per unit electron pressure decreases, whereas the photodetachment cross section increases above γ 5500 Å and decreases slightly below this wavelength. The overall effect is that the absorption coefficient is increased at large wavelengths and decreased at small wavelengths due to interparticle interaction. The effect of perturbers on absorption coefficient is found to be smaller for ion-sphere approximation than that for Debye-Hückel approximation.