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

29th International Conference on Photonic, Electronic, and Atomic Collisions

Wu, Z.W.^1,2 ; Surzhykov, A.^1 ; Kabachnik, N.M.^3,4 ; Dong, C.Z.^2 ; Fritzsche, S.^1,5

Helmholtz-Institut Jena, Fröbelstieg 3, Jena

D-07743, Germany^1

Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou

730070, China^2

European XFEL, Albert-Einstein-Ring 19, Hamburg

D-22761, Germany^3

Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow

119991, Russia^4

Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, Jena

D-07743, Germany^5

关键词: Degree of polarization;    Density matrix theory;    Highly charged ions;    Isoelectronic sequence;    Linear polarization;    Multiconfiguration Dirac-Fock method;    Overlapping resonances;    Polarization measurements;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/635/1/012020/pdf
DOI  :  10.1088/1742-6596/635/1/012020

来源: IOP

【 摘 要 】

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 1s2p2Ji= 3/2 → 1s2s2p J = 1/2, 3/2 + γ1→ 1s22s Jf= 1/2 + γ1+ γ2radiative cascade of lithium-like W71+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 Δω0.2 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.