The contribution of the magnetic quadrupole to the angular distribution and polarization of electron-impact excitation and dielectronic recombination in highly charged ions

Abstract

The degree of linear polarization and angular distribution of the x-ray photoemission of highly charged He-like and Li-like uranium ions following electron-impact excitation and dielectronic recombination processes are calculated using a fully relativistic distorted-wave method. A detailed investigation is carried out regarding the contribution of the magnetic quadropole (M2) term to the subsequent characteristic x-ray emission from the above two different processes. It is found that while the M2 term has a slight effect on the angular distribution and linear polarization of electron-impact excitation, it has a substantial effect on the same properties of dielectronic recombination.

Calculation of differential cross section for dielectronic recombination with two-electron uranium

“…Figs. [6][7][8] show that Stokes parameters also very sensitive to Breit interaction. For nonpolarized incident electrons the corresponding polarizations of the emitted photon give equal contributions to the differential cross sections σ 45 • , σ 135 • and σ − , σ + , respectively.…”

“…The influence of the Breit and QED effects on the radiative transition parameters is analyzed in detail. Dielectronic recombination with two-electron uranium ion was also studied theoretically in [8] In particular, the linear polarization and angular distribution of the x-ray photoemission was studied, contribution of the magnetic quadrupoles was investigated.…”

Polarization measurement of dielectronic recombination transitions in highly charged krypton ions

“…The present work also demonstrates the application of the Compton polarimetry technique, which provides advantages over Bragg polarimetry, previously used for DR polarization measurements at EBITs [23][24][25], by measuring both the degree and the angle of polarization and by being applicable in a broad range of energies. This technique can also be applied to investigate polarization properties of other electron-ion collision processes such as resonant recombination [38,66] and excitation, radiative recombination [36,67,68], electron impact excitation [26][27][28][29][30][31][32]69], nuclear-field-induced excitation [70] and higher-order resonant recombination processes [71,72]. Due to its high sensitivity, Compton polarimetry can also be used for studies of weak radiative transitions, or, alternatively, for high accuracy studies of stronger transitions, in particular of those sensitive to effects of quantum electrodynamics [73].…”

State-selective influence of the Breit interaction on the angular distribution of emitted photons following dielectronic recombination

“…We give here a brief description of the theoretical framework used for describing the DR in few-electron ions, as this process has already been extensively discussed in the literature [15,[35][36][37]. Due to the collision of unidirectional electrons with the ions in the present setup, the formed resonant states are aligned along the beam axis, i.e., the magnetic sublevel population of a resonant state |α d J d M d is non-statistically distributed.…”