Linear polarization of x-ray transitions due to dielectronic recombination in highly charged ions

Jörg, Holger; Hu, Zhimin; Bekker, Hendrik; Blessenohl, Michael A.; Hollain, Daniel; Fritzsche, S.; Surzhykov, A.; López‐Urrutia, J. R. Crespo; Tashenov, S.

doi:10.1103/physreva.91.042705

Cited by 43 publications

(23 citation statements)

References 89 publications

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“…DR is sensitive to the Breit interaction [48,69,[81][82][83][84] in both the angular distribution and the linear polarization of the emitted x rays [81]. These properties were measured only for a few resonances in heavy ions [48,50,85,86], and no systematic studies of the alignment in DR, TR or QR were reported.…”

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Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

et al. 2016

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We studied angular distributions of x rays emitted in resonant recombination of highly charged iron and krypton ions, resolving dielectronic, trielectronic, and quadruelectronic channels. A tunable electron beam drove these processes, inducing x rays registered by two detectors mounted along and perpendicular to the beam axis. The measured emission asymmetries comprehensively benchmarked full-order atomic calculations. We conclude that accurate polarization diagnostics of hot plasmas can only be obtained under the premise of inclusion of higher-order processes that were neglected in earlier work. 32.30.Rj, 31.30.jc, 34.80.Lx The observation of x-ray polarization in emissions from the Crab Nebula [1,2], with synchrotron radiation as its origin, fueled a strong interest in the astrophysics community for launching an x-ray polarimetry (XRP) mission [3][4][5][6][7]. X-ray Imaging Polarimetry Explorer (XIPE) has recently been selected as one of three candidates for the next medium-size satellite mission by the European Space Agency ESA. Its aim is studying the anisotropies of astrophysical plasmas which are found in the most extreme yet poorly understood sites in the Universe [8,9]. Up to now anisotropic plasmas were found in active galactic nuclei [10][11][12], pulsars [13], gamma-ray bursts [14][15][16], neutron stars [17,18], and solar flares [19][20][21]. They appear prominently also in the laboratory: in experiments with strong lasers [22,23], magnetic cusps [24], z -pinches [25], and fusion devices [25][26][27] such as tokamaks [28][29][30] and stellarators. The directionality of the electron-ion collisions leaves an imprint in the polarization of the plasma x rays [31][32][33][34][35][36]. Polarization measurements may therefore reveal the presence and orientation of particle beams, magnetic fields and, hence, provide information on the plasma heating and confinement mechanisms [25][26][27] in instances where spatial resolution is insufficient. In astrophysics, indeed, XRP is often the only technique for deriving information on the geometry of angularly unresolved sources [8,37].Ideally, the XRP data should be analyzed with detailed knowledge of the atomic polarization mechanisms. Until now, however, no or little experimental information is available for most atomic processes. Only very few studies of x-ray polarization and angular distributions have been performed for astrophysically relevant ions using electron beam ion traps (EBITs) [38][39][40][41][42][43][44][45][46]. Other studies with EBITs [47][48][49][50], electron accelerators [32, 51, 52] and storage ring [34,53] have focused on heavy ionic systems. Moreover, the photoelectric gas polarimeter [4,54] of the XIPE mission will not resolve individual x-ray transitions. This limitation is rather general, even if high resolution detectors were used, since Doppler shifts will most likely blur the signal. Thus, the polarization signal will contain contributions from many transitions and continuum radiation due to bremsstrahlung and recombination of plas...

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Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

et al. 2016

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“…Recently, the polarization of DR Kα x rays from highly charged Kr and Xe were measured with a novel Compton polarimeter [16,33]. The degree of linear polarization was determined for a few DR resonances and showed agreement with theoretical predictions of a measurable influence of the Breit interaction (BI).…”

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

et al. 2017

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We report a measurement of KLL dielectronic recombination in charge states from Kr⁺³⁴ through Kr⁺²⁸ in order to investigate the contribution of the Breit interaction for a wide range of resonant states. Highly charged Kr ions were produced in an electron-beam ion trap, while the electron-ion collision energy was scanned over a range of dielectronic recombination resonances. The subsequent Kα x rays were recorded both along and perpendicular to the electron-beam axis, which allowed the observation of the influence of the Breit interaction on the angular distribution of the x rays. Experimental results are in good agreement with distorted-wave calculations. We demonstrate, both theoretically and experimentally, that there is a strong state-selective influence of the Breit interaction that can be traced back to the angular and radial properties of the wave functions in the dielectronic capture

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“…≈ 5.4 eV. Since the degree of linear polarization can be measured quite easily nowadays for a wide range of photon energies by using the techniques of Compton polarimetry [18], such accurate polarization measurements on the γ 2 photons may be used to explore the level-splitting of HCIs.…”

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Linear polarization of x-rays emitted in the decay of highly-charged ions via overlapping resonances

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et al. 2015

J. Phys.: Conf. Ser.

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View the article online for updates and enhancements. Related contentHigh-precision mass measurements for fundamental applications using highlycharged ions with SMILETRAP Sz Nagy, T Fritioff, I Bergström et al. Abstract. The linear polarization of x-rays, emitted from highly-charged ions, has been studied within the framework of the density matrix theory and the multiconfiguration Dirac-Fock method. Emphasis was placed especially on two-photon cascades that proceed via intermediate overlapping resonances. For such two-step cascades, we here explore how the level-splitting of the resonances affects the linear polarization of the x-rays, and whether modifications in the degree of polarization may help determine small level-splittings in multiply-and highly-charged ions, if carefully analyzed along isoelectronic sequences. Detailed calculations are carried out for the 1s2p 2 Ji = 3/2 → 1s2s2p J = 1/2, 3/2 + γ1 → 1s 2 2s J f = 1/2 + γ1 + γ2 radiative cascade of lithium-like W 71+ ions. For this cascade, a quite remarkable increase of the (degree of) linear polarization is found for the second-step γ2 photons, if the level-splitting becomes smaller than ∆ω 0.2 a.u. ≈ 5.4 eV. Accurate polarization measurements of x-rays may therefore be also utilized in the future to ascertain small level-splittings in multiply-and highly-charged ions.

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Linear polarization of x-ray transitions due to dielectronic recombination in highly charged ions

Cited by 43 publications

References 89 publications

Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

Strong higher-order resonant contributions to x-ray line polarization in hot plasmas

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

Linear polarization of x-rays emitted in the decay of highly-charged ions via overlapping resonances

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