Alignment of L ₃ subshell vacancy states created without Coster–Kronig decay through the selective photoionization in ₈₂Pb, ₉₀Th and ₉₂U and effect of external magnetic field

Abstract

Alignment of the L ₃ (J = 3∕2) subshell vacancy states produced following selective photoionization in the L ₃ subshells of the ₈₂Pb, ₉₀Th and ₉₂U elements have been investigated through the angular distribution measurements of the emitted L ₃ subshell X-ray lines. The L ₃ subshell of ₈₂Pb, ₉₀Th and ₉₂U elements were excited by the incident K X-rays of ₃₇Rb, ₄₁Nb and ₄₂Mo elements from secondary targets, respectively. The K X-rays were obtained from the secondary targets excited by the unpolarized 59.54 keV photons obtained from ²⁴¹Am point source. The measurements were performed with tri-axial experimental setup over the angular range 90–154^∘ by moving the source and keeping the target-detector assembly fixed. The error in the normalization of the L ₃ subshell X-rays were removed through the uniform mixing of the reference element into primary element and the simultaneous detection of the L ₃ (J = 3∕2) subshell X-rays from primary element and isotropically emitted K (J = 1∕2) X-rays from reference element without disturbing the experimental setup. The incident photon energy (E _in ) from secondary target were selected in such way that B _L3 < E _in < B _L2, B _Li (i = 1–3) being the binding energy of L _i subshell. The selective photoionization leads to reduction in the observed anisotropy due to shifting of unaligned vacancies fromthe L ₁ and L ₂ (J = 1∕2) subshells to the L ₃ subshell (J = 3∕2) through the Coster–Kronig (CK) transitions. The present measurements undoubtedly conclude that anisotropy in the L ₃ subshell X-ray emission, if present, is at the most of the order of theoretical evaluated value. The alignment measurements with and without applied external magnetic field (~0.6 T) does not significantly change the emission of the L ₃ subshell X-rays.

Graphical abstract