Effects of angular-momentum-changing collisions on dielectronic satellite spectra

A generalization of the conventional low-density corona-model theory is presented for determining the population densities of autoionizing levels in multiply charged ions and the intensities of satellite lines, produced by radiative transitions from these levels, which are associated with the resonance lines in the x-ray emission spectra of high-temperature plasmas. In addition to the usual processes of radiationless electron capture, inner-shell electron collisional excitation, autoionization, and radiative decay, account is taken of collisional transitions between the autoionizing levels. Results of calculations are presented to illustrate the effects of angular-momentum-changing electron collisions on the intensities of the satellites to the $1s2p{}_{}{}^1{}_{}{}^{}P\to 1s^2{}_{}{}^1{}_{}{}^{}S$ resonance line of the heliumlike ions AlXII and SiXII which are produced by the transitions $1s2pnl\to 1s^2\mathrm{nl}$ with $n=2\mathrm{}$ in the corresponding lithiumlike ions. Distorted-wave calculations have been carried out in an $\mathrm{LS}$ coupling scheme with configuration mixing for the autoionization, radiative decay, and electron collision rates. The generalized emission rate coefficients describing dielectronic recombination and inner-shell electron collisional excitation are tabulated as functions of electron density as well as temperature. The intensity of the satellite line emitted in the $1s2p^2{}_{}{}^2{}_{}{}^{}D\to 1s^{2}2p{}_{}{}^2{}_{}{}^{}P$ transition, which is the strongest at low densities, is found to be practically unaffected by electron collisional transitions between the autoionizing levels and remains a function mainly of temperature up to a density as high as ${10}^{24}$ ${\mathrm{cm}}^{-3\mathrm{}}$. However, for electron densities exceeding only ${10}^{22}$ ${\mathrm{cm}}^{-3\mathrm{}}$, the inclusion of these collisional processes causes a significant increase in the intensity of the $1s2p^2{}_{}{}^2{}_{}{}^{}P\to 1s^{2}2p{}_{}{}^2{}_{}{}^{}P$ satellite line, which is relatively weak at lower densities, and produces an enhancement of the total intensity of the radiation emitted in all of the $n=2\mathrm{}$ satellite transitions. The strong electron density dependence of the ratio of these two satellite-line intensities may be useful in the spectroscopic determination of the densities in compressed plasmas.