Experimental Demonstration of the Breit Interaction which Dominates the Angular Distribution of X-ray Emission in Dielectronic Recombination

Abstract

We report the experimentally determined angular distribution of the [1s2s(2)2p(1/2)](1)→[1s(2)2s(2)](0) transition in dielectronic recombination of Li-like Au. Recently, Fritzsche et al. [Phys. Rev. Lett. 103, 113001 (2009)] predicted that the Breit interaction plays a dominant role in the angular distribution of this transition. However, the predicted phenomenon has not yet been observed experimentally due to technical difficulties in conventional methods. To overcome the difficulties, we combine two different measurements with an electron beam ion trap (EBIT) to obtain the x-ray angular distribution. One is the x-ray measurement at 90° and another is the integral resonant strength measurement through the ion charge abundance in the EBIT. Our measurements agree well with the theoretical prediction and confirm the dominance of the Breit interaction.

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

“…The red curve in the upper plot corresponds to calculation of the total cross section within dipole approximation where only terms with j 0 = 1 are taken into account in the multipole expansion Eq. (17). The black curve in the upper plot corresponds to the full calculation (j 0 ≤ 9).…”

“…The recent studies showed that the Breit interaction may give important and even dominant contribution to the cross section of the dielectronic recombination with few-electron highly charged ions [9,[13][14][15][16][17][18].…”

Electron Impact Excitation and Dielectronic Recombination of Highly Charged Tungsten Ions

“…However, to the best of our knowledge, there are few work about the linear polarization of tungsten X-ray emissions in ITER fusion plasmas. Since angle-resolved observables, such as linear polarization and angular distribution, are much more sensitive to various atomic effects and physical variables than the total (angle-averaged) decay rates of X-ray emissions, the angle-resolved studies of X-rays have been used to extract a variety of physical effects in the last few decades [30][31][32][33][34][35][36]. For those strong X-ray emissions from tungsten ions, they are hardly affected by the radiative damping caused by additional atomic excitation processes [27] and, thus, are relatively clean atomic radiations, which could be used to study the angle-resolved observables to reveal the population mechanism of excited levels [37,38] and perhaps to reflect plasma conditions.…”

Measurements of density dependent intensity ratios of extreme ultraviolet line emission from Fe X, XI, and XII

“…The measured intensity of the emitted radiation from these ions strongly depends on the angle of observation relative to the beam axis. There have been several studies reported in the literature for the polarization of radiation emitted from ions trapped in an EBIT (Henderson et al 1990;Beiersdorfer et al 1996;Taḱacs et al 1996;Gu et al 1999;Liang et al 2009a;Hu et al 2014b;Shah et al 2015). In the present study, we measured EUV spectra using CoBIT at 90…”