Dynamic polarizability of an atomic ion within a dense plasma

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 1s(2 1)S→1s2p(1)P) for the ground state 1s(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 1s(2 1)S→1s2p(1)P absorption oscillator strength in the atomic ion within dense plasmas.