Angular dependence of L₃-subshell X-ray emission following photoionisation

L₃-subshell alignment of Th and U ionized by 59.5 keV photons has been investigated by evaluating the angular dependence of L{i}(i=l, α, η, β and γ) X-ray lines. The angular dependence measurements were performed by measuring the fluorescence cross section, σ{Li}(i=1, η, α, β and γ) and σ{Ll}/σ{Lγ}, σ{Lη}/σ{Lγ }, σ{Lα}/σ{Lγ } and σ{Lβ}/σ{Lγ} ratios at different angles. It was observed from the measurements that L{i}(i=l and α) X rays for the L₃-subshell depended on the emission angle and had an anisotropic spatial distribution. On the other hand, there was no dependence of emission angle and any significant anisotropy for other L X rays. The both Ll and Lα X-rays originate from the filling of vacancies in states L₃-subshell with J =3/2. The results of measurements indicate that the L₃-subshell vacancy states with J = 3/2 are aligned, whereas L{1}, and L{2}vacancy states with J =1/2 are non-aligned. Integral cross-sections for the L{i}(i=l, η, α, β and γ) X-rays and L subshell fluorescence yields ω{i} (i= 1, 2 and 3) were also determined and results were compared with theoretically calculated values and results of others and fairly good correspondence was observed.