Linear polarization of the characteristic x-ray lines following inner-shell photoionization of tungsten

Abstract

The linear polarization of the characteristic lines $L{\ensuremath{\alpha}}_{1}$ $(3{d}_{5/2}\ensuremath{\rightarrow}2{p}_{3/2})$ and $L{\ensuremath{\alpha}}_{2}$ $(3{d}_{3/2}\ensuremath{\rightarrow}2{p}_{3/2})$, following inner-shell photoionization of neutral tungsten, is analyzed both experimentally and theoretically. In the experiment, a tungsten target is photoionized by the primary emission of an x-ray tube with incident photon energies in the range of 10.2--30 keV. The $\ensuremath{\sigma}$ and $\ensuremath{\pi}$ components of the emitted fluorescence are measured by using a spectropolarimeter, based on x-ray diffraction at Bragg angles close to ${45}^{\ensuremath{\circ}}$. The degree of linear polarization of the $L{\ensuremath{\alpha}}_{1}$ and $L{\ensuremath{\alpha}}_{2}$ lines is determined to be $+(1.6\ifmmode\pm\else\textpm\fi{}0.5)%$ and $\ensuremath{-}(7\ifmmode\pm\else\textpm\fi{}2)%$, respectively. In addition, this degree of polarization is calculated within the framework of the density-matrix theory as a function of the incident photon energy. These calculations are in good agreement with the experimental results and show only a weak dependence of the degree of polarization on the energy of the incident photoionizing photon.