Effects of angular-momentum-changing electron collisions and radiative corrections on dielectronic satellite spectra

The conventional low-density isolated-resonance theory for the intensities and widths of the 2l’2l’ ’→1s2l and the 1s2l’2l’ ’→1$s^2$2l dielectronic satellite lines has been generalized to take into account angular-momentum-changing electron collisions and the interaction between the atomic system and the quantized radiation field. The electron collisional transitions alter the population densities of the autoionizing levels, while the atom-field interaction modifies the relative probabilities for autoionization and radiative decay. The modifications to the conventional low-density expression for the satellite-line intensities may be interpreted as interference between the resonant and nonresonant electron continua together with radiative corrections. These modifications have been expressed in terms of the unperturbed decay rates, the photoionization cross sections, and the Fano line-profile parameters. Using the transition probabilities obtained from two different relativistic atomic structure codes, the K-shell satellite-line intensities and widths have been calculated for argon as functions of temperature and density, taking into account both dielectronic recombination and inner-shell-electron collisional excitation. The combined effects of relativity, radiative corrections, and angular-momentum-changing electron collisions are predicted to be most significant for radiative transitions from the 2$p^2$ ${}^3$P and 1s2$p^2$ ${}^2$P metastable autoionizing states, which give rise to satellite lines that are relatively weak at low densities but are among the most prominent spectral features in high-density plasmas.