Linear polarization of L₃ sub-shell X-ray lines for some high-Z elements

In this paper, the degree of polarization of the fluorescent L X-ray lines \( L_{\ell } \) $L_{\ell }$ , L_α1 and L_α2, is studied theoretically with respect to incident energy for some high-Z elements from tungsten to Uranium. The linear polarization for each characteristic line is evolved through alignment parameter assessed by nonrelativistic dipole approximation (NDA) in a point Coulomb potential (A₂₀), and accommodating the effect of screening in a screened Coulomb potential (A₂₀^*) and analytical perturbation theory (A₂₀**). The values of degree of linear polarization predicted using alignment parameters (A_20, A₂₀^*and A₂₀^**) are not exactly the same as reported by Kämpfer et al. (Phys Rev A 93:033409, 2016) but the trends are almost the same. Since alignment is model sensitive, therefore, the degree of linear polarization will also be dependent on the theoretical approximation/model used. For \( L_{\ell } \) $L_{\ell }$ lines, polarization is found to be in the range (12 to 43) %, whereas for the L_α1 line, the ultimate vigorous line of the L-shell emission, the estimated polarization is positive with value range from (+ 2.5 to + 7.5)% and for the L_α2 line the polarization is negative with value range from (− 9.5 to − 27) %. These calculations are in exemplary compromise with the earlier theoretical results and manifest barely a feeble vulnerability of polarization on the vibrancy of the incident radiation. The present polarization trends show resemblance with the results of Kämpfer et al. (2016) and Özdemir et al. (Appl Radiat Isotopes 69:991, 2011), although the values are not absolutely matching.