Angular dependence of L-3 x-ray emission following L-3 sub-shell photoionization in Pb

The L1, L alpha and L beta (2,5,6,7,15) x-ray fluorescence (XRF) differenti al cross-sections in Pb were measured at the 13.6 keV incident photon energ y (E-L3 < E-inc < E-L2, E-Li being the L-i sub-shell binding energy) and in the angular range 90-160 degrees. At this incident photon energy, the L-3 sub-shell vacancies (J = 3/2) are produced only due to the direct ionizatio n and the reduction in the observed anisotropy in the emission of the L1, L alpha and L beta (2,5,6,7,15) x-rays due to the transfer of unaligned L-1 and L-2 sub-shell vacancies (J = 1/2) to the L-3 sub-shell through Coster-K ronig transitions is eliminated. The measurements were performed using Rb s econdary exciter in conjunction with the Am-241 primary exciter as photon s ource and a Si(Li) detector. The differential cross-sections for various x- rays were found to be angle-independent within experimental error. Integral cross-sections for the L1, L alpha and L beta (2,5,6,7,15) x-rays were als o deduced and were found to be in agreement with those evaluated using the most reliable theoretical values of L-3 sub-shell photoionization cross-sec tion, fluorescence yield and x-ray emission rates. Copyright (C) 2001 John Wiley & Sons, Ltd.