Regular Article

Alignment of L₃ subshell vacancy states created without Coster–Kronig decay through the selective photoionization in ₈₂Pb, ₉₀Th and ₉₂U and effect of external magnetic field

¹ Department of Physics, Punjabi University, Patiala 147002, India
² Department of Physics, Panjab University, Chandigarh 160014, India
³ Department of Physics, GGDSD College, Chandigarh 160030, India
⁴ Department of Physics, IKG Punjab Technical University, Kapurthala 144601, India

^a e-mail: gurjeets59@gmail.com

Received: 24 May 2017
Published online: 10 October 2017

Abstract

Alignment of the L₃ (J = 3∕2) subshell vacancy states produced following selective photoionization in the L₃ subshells of the ₈₂Pb, ₉₀Th and ₉₂U elements have been investigated through the angular distribution measurements of the emitted L₃ subshell X-ray lines. The L₃ 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 L₃ subshell X-rays were removed through the uniform mixing of the reference element into primary element and the simultaneous detection of the L₃ (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 L₁ and L₂ (J = 1∕2) subshells to the L₃ subshell (J = 3∕2) through the Coster–Kronig (CK) transitions. The present measurements undoubtedly conclude that anisotropy in the L₃ 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 L₃ subshell X-rays.