Polarization measurement of dielectronic recombination transitions in highly charged krypton ions

Abstract

We report linear polarization measurements of x rays emitted due to dielectronic recombination into highly charged krypton ions. The ions in the He-like through O-like charge states were populated in an electron beam ion trap with the electron beam energy adjusted to recombination resonances in order to produce K α x rays. The x rays were detected with a newly developed Compton polarimeter using a beryllium scattering target and 12 silicon x-ray detector diodes sampling the azimuthal distribution of the scattered x rays. The extracted degrees of linear polarization of several dielectronic recombination transitions agree with results of relativistic distorted-wave calculations. We also demonstrate a high sensitivity of the polarization to the Breit interaction, which is remarkable for a medium-Z element like krypton. The experimental results can be used for polarization diagnostics of hot astrophysical and laboratory fusion plasmas.

Importance of the Breit interaction for calculation of the differential cross section for dielectronic recombination with one-electron uranium

“…10. Recently, photon emission asymmetries were measured with high accuracy for radiative electron recombination with few-electron Fe ions [15]. The presented calculation shows the large sensibility of the photon emission asymmetry to the Breit interaction.…”

“…The recent studies revealed that the Breit interaction may give an "laywer92@mail.ru important and even dominant contribution to the cross section of the dielectronic recombination with few-electron highly charged ions [5,[11][12][13][14][15],…”

Investigation of the intershell higher order resonant recombination and polarization of X‐ray emission of B‐like silicon ions

“…Thus, X‐ray radiation from the intershell resonant recombination process is anisotropic and polarized . For an electric dipole (E1) transition, the degree of linear polarization of X‐ray emission can be expressed as follows: where A 2 is the alignment parameter used to describe the nonstatistical magnetic sublevel population of the intermediate resonance state. Following the density matrix theory, for the resonant capture of an unpolarized electron, the alignment parameter can be expressed as follows: where M is the magnetic quantum number, the quantity in large parentheses represents the Wigner 3‐ j symbol, σ M is the resonant capture cross sections from the initial state to the magnetic sublevels of the intermediate excited state, normalized such that .…”

“…Following the density matrix theory, for the resonant capture of an unpolarized electron, the alignment parameter can be expressed as follows: where M is the magnetic quantum number, the quantity in large parentheses represents the Wigner 3‐ j symbol, σ M is the resonant capture cross sections from the initial state to the magnetic sublevels of the intermediate excited state, normalized such that . in Equation is an intrinsic anisotropy parameter that is completely determined by the total angular momentum of the intermediate excited state J d and the final state J f and can be expressed as follows: where the quantity in the large parentheses denotes the wigner 6‐ j symbol.…”

Resonance strengths for KLL dielectronic recombination of highly charged mercury ions and improved empirical Z -scaling law

“…Since the resonant excitation in DR is solely evoked by the interaction of the active electrons, the experimental determination of cross sections provides one new insights into relativistic electron interactions in a dynamical process. Recently, the experiments became sensitive to the contribution of the generalized Breit interaction [23,36] to DR resonance strengths, as well as to the linear polarization of x rays emitted during DR [37,38]. Also, the theoretical description of the process requires non-trivial additions to the many-body theory of atomic structures.…”