Dominance of the density effects in the magnetic sublevel population and circular polarization of x-ray radiation

Abstract

On the basis of the fully relativistic distorted-wave treatment of impact excitation by a longitudinally polarized electron beam, we have assessed the influence of density effects on the magnetic sublevel population and circular polarization of x-ray radiation, taking the 1s2p 3P2 1s2 1S0 line of selected He-like Ne8+, Ar16+, and Kr34+ ions as an example. Starting from the most general method of rate equation, we carried out specific analytic expressions in terms of the magnetic sublevel-to-magnetic sublevel collisional-radiative model, corresponding to different states. It is shown that the density contributions to the magnetic sublevel population can be considerable. These dramatic influences also lead to a remarkable decrease in the circular polarization of x-ray radiation, yet the character of which weakens as the incident energy and/or atomic number increases. The Breit interaction and radiative cascade contributions are also estimated, and found to be generally important in these systems. These findings originate a better understanding of the fundamentals of x-ray radiation arising from various kinds of plasmas. Comparisons of our results with other theoretical predictions, when available, are made.

Local time dependence of the magnetic sublevel population and polarization of fluorescence radiation

“…Here, k runs over all the high Rydberg states D J M k k k . It should be mentioned that although the generated atomic data and longitudinally polarized EIE collision strengths are similar to our recent study [6], the densitydependent time evolution models and the details in calculation (code) are completely different to those used before.…”

“…The polarization of fluorescence emission produced in highly charged ion collisions with an electron beam contains a wealth of information on the magnetic sublevel population. It has not only led to key advances in the diagnosis of various kinds of plasmas, but contributed to our insight into the behavior of collision processes in novel environments [1][2][3][4][5][6]. Compared with conventional cross-section, such polarization has served as the bridge to, and touchstone for, better understanding of collision dynamics and has been found to be a powerful tool for spectroscopy.…”

“…In practice, however, very little is still known of how these effects affect the populations of magnetic sublevels within individual fine-structure levels of ions or, how the (population distribution of) atomic levels determine polarization and the angular distribution of subsequently emitted radiation. In our recent work [6], we investigated the density effects upon the magnetic sublevel population and polarization of secondary radiation emitted by the longitudinally polarized EIE of highly charged ions. In that case, we mainly discussed the contributions of BI and radiative cascade for the systems in a steady state.…”

Density dependence of intensity ratios of the 3d → 2p x-ray anisotropic emission from electron-beam excited Ar13+ ions

“…Finally, let us mention that in this work, we have limited our attention to plasmas in the steady state, but it would be interesting to extend the present theoretical model to investigate the time dependence of R over short time scales characterizing atomic processes. Such an extension is expected to provide a deeper insight on the atomic structure of ions and their interactions with free electrons [39,40].…”

Relaxation effects on the magnetic cross section and fluorescence radiation polarization after 4d inner-shell photoionization of Ba-like ions

“…The polarization can find wide application in many astrophysical objects, for example, magnetized neutron stars, accretion disks and so on. Such polarization can also provides unique possibilities for probing physical effects in the radiation field and, in fact, serves as a bridge to, better understanding of the e-p interaction [32][33][34][35][36][37][38][39]. The theoretical performance is, therefore, not merely a wish but a necessity.…”