近日，西北师范大学的武中文及其研究团队取得一项新进展。他们揭示了类锂离子共振电子俘获后光子发射线性极化的自旋极化效应。相关研究成果已于2024年11月4日在国际知名学术期刊《物理评论A》上发表。

该研究团队在密度矩阵理论框架下，研究了高电荷离子与自旋极化电子的双电子复合（DR）过程。特别关注了复合电子的自旋极化如何影响后续光子发射的极化行为。为解决这一问题，研究人员提出了一种适用于任意离子任意DR过程的一般密度矩阵形式，并将其应用于类锂离子的一个特定DR过程（即 1s² 2s J?=1/2 + εe? → 1s 2s² 2p½ J?=1 → 1s² 2s J?=0 + γ）作为示例。

对于这个特定过程，研究人员利用多组态Dirac-Hartree-Fock方法，对复合电子的不同自旋极化状态进行了详细计算。结果发现，复合电子的自旋极化对光子发射的线性极化P?（即第一Stokes参数）几乎没有影响，而极化P?（即第二Stokes参数）则强烈依赖于自旋极化。

此外，由于P?和P?的数值差异较大，导致获得了较大的极化倾斜角，该角度受到自旋极化的显著影响，尤其是在前向和后向光子发射时。这些极化行为与在高电荷离子与极化电子的辐射复合中获得的结果非常相似[Maiorova等人，Phys. Rev. A 107, 042814 (2023)]，并且可以使用现代X射线偏振计轻松观察到。

根据所获得的强烈依赖性，研究人员建议通过精确测量极化行为来诊断电子束的自旋极化状态，这种方法由于双电子复合（DR）过程的共振特性，比辐射复合[Maiorova等人，Phys. Rev. A 107, 042814 (2023)]的情况更为可行且具有前景。

附：英文原文

Title: Spin polarization effect on linear polarization of photon emission following resonant electron capture of lithiumlike ions

Author: Z. W. Wu, Y. Z. Wang

Issue&Volume: 2024/11/04

Abstract: Dielectronic recombination (DR) of highly charged ions with spin-polarized electrons is studied within the framework of density-matrix theory. Special attention is paid to the question of how spin polarization of the recombined electron affects the polarization behavior of the subsequent photon emission. To address this question, while a general density-matrix formalism applicable to any DR process of arbitrary ions is presented, here, it is applied to a particular DR process (i.e., 1s² 2s J?=1/2 + εe? → 1s 2s² 2p½ J?=1 → 1s² 2s J?=0 + γ) of lithiumlike ions as an example. For this particular process, detailed calculations are carried out for different spin polarization states of the recombined electron by utilizing the multiconfigurational Dirac-Hartree-Fock method. It is found that the spin polarization of the recombined electron hardly affects the linear polarization P₁ (i.e., the first Stokes parameter) of the photon emission, whereas the polarization P₂ (i.e., the second Stokes parameter) depends strongly on the spin polarization. In addition, owing to big differences in the magnitudes of P₁ and P₂, a large polarization tilt angle is obtained that is remarkably affected by the spin polarization, especially for the forward and backward photon emission. These polarization behaviors are found to be rather similar to the results obtained in radiative recombination of highly charged ions with polarized electrons [Maiorova et al., Phys. Rev. A 107, 042814 (2023)] and can be readily observed using modern x-ray polarimeters. Based on the strong dependences obtained, we suggest that accurate measurements of the polarization behaviors can be applied to diagnosing the spin polarization state of electron beams, which is more feasible and promising than the case of radiative recombination [Maiorova et al., Phys. Rev. A 107, 042814 (2023)] owing to the resonance nature of DR processes.

DOI: 10.1103/PhysRevA.110.052803

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.052803