Collective excitation transfer effect in dielectric susceptibility

Abstract

The combined effect of two collective processes in the resonant dielectric susceptibility is investigated. The first is the coherent excitation transfer process, which gives rise to the Lorentz–Lorenz shift. The second is the many body shielding of the resonant interaction between the atoms. The combined treatment of these effects leads to a qualitatively different behaviour of the susceptibility of a high density gas. The frequency dependence of the susceptibility is obtained from the detailed numerical solution of the self-consistent equations. In the quasi-static limit, an analytical solution is also obtained. In this limit, the result depends upon two parameters: one proportional to the gas density, and the other proportional to the square root of it.