Dynamic polarizability of an atomic ion within a dense plasma

Joyee Basu and Debasis Ray

Phys. Rev. E 83, 016407 – Published 31 January 2011

Abstract

We analyze the influence of plasma electron density on frequency-dependent linear field-response behavior of an atomic ion embedded in a dense plasma medium. The frequency-dependent atomic response, characterized by the dynamic dipole polarizability $α$ $_{d}$ (ω) as a function of the angular frequency ω of the time-dependent field, is estimated here up to the first pole of $α$ $_{d}$ (ω) on the ω axis (corresponding to the lowest resonance transition $1 s^{2}^{1} S \to 1 s 2 p^{1} P$ ) for the ground state $1 s^{2}^{1} S$ of a two-electron atomic ion Ne $^{8 +}$ ( $Z$ = 10) at different plasma electron densities, as a typical example, employing the time-dependent coupled Hartree-Fock scheme within the framework of the ion-sphere model. It is observed that, owing to plasma density-induced enhancement of $α$ $_{d}$ (ω) at every ω, the pole position of $α$ $_{d}$ (ω) on the ω axis retracts toward the origin. This indicates a density-induced lowering (redshift) of the corresponding transition energy that conforms to experimentally observed trends. The polarizability calculation suggests a density-induced drop in the $1 s^{2}^{1} S \to 1 s 2 p^{1} P$ absorption oscillator strength in the atomic ion within dense plasmas.