Direct Determination of the Magnetic Quadrupole Contribution to the Lyman-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>α</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:math>Transition in a Hydrogenlike Ion

Weber, G.; Bräuning, H.; Surzhykov, A.; Brandau, C.; Fritzsche, S.; Geyer, Sabrina; Hagmann, S.; Heß, Sebastian; Kozhuharov, C.; Märtin, R.; Petridis, N.; Reuschl, R.; Spillmann, U.; Trotsenko, S.; Winters, D.; Stöhlker, Th.

doi:10.1103/physrevlett.105.243002

Cited by 82 publications

(47 citation statements)

References 23 publications

(45 reference statements)

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“…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.…”

Section: Introductionmentioning

confidence: 99%

Electron Impact Excitation and Dielectronic Recombination of Highly Charged Tungsten Ions

et al. 2015

Atoms

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Electron impact excitation (EIE) and dielectronic recombination (DR) of tungsten ions are basic atomic processes in nuclear fusion plasmas of the International Thermonuclear Experimental Reactor (ITER) tokamak. Detailed investigation of such processes is essential for modeling and diagnosing future fusion experiments performed on the ITER. In the present work, we studied total and partial electron-impact excitation (EIE) and DR cross-sections of highly charged tungsten ions by using the multiconfiguration Dirac-Fock method. The degrees of linear polarization of the subsequent X-ray emissions from unequally-populated magnetic sub-levels of these ions were estimated. It is found that the degrees of linear polarization of the same transition lines, but populated respectively by the EIE and DR processes, are very different, which makes diagnosis of the formation mechanism of X-ray emissions possible. In addition, with the help of the flexible atomic code on the basis of the relativistic configuration interaction method, DR rate coefficients of highly charged W 37+ to W 46+ ions are also studied, because of the importance in the ionization equilibrium of tungsten plasmas under running conditions of the ITER.

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Section: Introductionmentioning

confidence: 99%

Electron Impact Excitation and Dielectronic Recombination of Highly Charged Tungsten Ions

et al. 2015

Atoms

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“…Since the x rays produced by the decay of individual magnetic sublevels are polarized differently, the measured degree of polarization probes the distribution of am [ 13,[49][50][51]. Although in some cases the polarization effects beyond the dipole approximation are important [26], for the sake of clarity we limit the discussion to the leading electricdipole approximation, which is adequate for the experimental accuracy of the present work. It can be shown that the degree of polarization is P(J = 1) = 3o;2(cro -e g ) V 2 + a 2(ob -o"i) P(J = 3/2) = , 3" 2(7 /2 °V2) , (2) in [15] and Eq.…”

Section: Resultsmentioning

confidence: 97%

“…Moreover, a number of experiments that measured the DR cross sections using electron beam ion traps (EBITs) had observed the DR x rays perpendicularly to the electron beam propagation direction [19][20][21][22][23][24][25], The interpretation of such experiments requires knowledge of the DR x-ray anisotropy and, thus, of its polarization. Furthermore, measurements of the x-ray emission anisotropy and polarization can comple ment each other to access effects beyond the electric-dipole approximation [26].…”

Section: Introductionmentioning

confidence: 99%

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

Jörg

Bekker

et al. 2015

Phys. Rev. A

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The linear polarization of x rays produced by dielectronic recombination into highly charged xenon ions was measured at an electron beam ion trap using the Compton polarimetry technique. This opens numerous possibilities for diagnostics of anisotropies of hot plasmas. Moreover, it was observed that the polarization of x rays, following the dielectronic capture populating the [1s2s²2p_1/2]₁ state, is highly sensitive to the Breit interaction. The experimental results for this transition rule out by 5σ calculations not taking the Breit interaction into account

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“…When compared to the total intensity of individual x-ray lines, angle-and polarizationresolved measurements have typically been found much more sensitive with regard to small (inner-) atomic interactions, such as the hyperfine structure [1,2], the Breit interaction [3,4,5], or the mixing of different multipoles of the radiation fields [6,7,8]. Until the present, however, the vast majority of such angle-and polarization-resolved studies were made for sufficiently well-isolated fine-structure levels, while little attention was paid so far to photon cascades via overlapping resonances.…”

Section: Introductionmentioning

confidence: 99%

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

Surzhykov

Кабачник

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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Direct Determination of the Magnetic Quadrupole Contribution to the Lyman-α1Transition in a Hydrogenlike Ion

Cited by 82 publications

References 23 publications

Electron Impact Excitation and Dielectronic Recombination of Highly Charged Tungsten Ions

Electron Impact Excitation and Dielectronic Recombination of Highly Charged Tungsten Ions

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

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

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