Angular dependence of L3 x‐ray emission following L3 sub‐shell photoionization in Pb

Abstract

AbstractThe Ll, Lα and Lβ2,5,6,7,15 x‐ray fluorescence (XRF) differential cross‐sections in Pb were measured at the 13.6 keV incident photon energy (EL3 < Einc < EL2, ELi being the Li sub‐shell binding energy) and in the angular range 90–160°. At this incident photon energy, the L3 sub‐shell vacancies (J = 3/2) are produced only due to the direct ionization and the reduction in the observed anisotropy in the emission of the Ll, Lα and Lβ2,5,6,7,15 x‐rays due to the transfer of unaligned L1 and L2 sub‐shell vacancies (J = 1/2) to the L3 sub‐shell through Coster–Kronig transitions is eliminated. The measurements were performed using Rb secondary exciter in conjunction with the 241Am primary exciter as photon source 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 Ll, Lα and Lβ2,5,6,7,15 x‐rays were also deduced and were found to be in agreement with those evaluated using the most reliable theoretical values of L3 sub‐shell photoionization cross‐section, fluorescence yield and x‐ray emission rates. Copyright © 2001 John Wiley & Sons, Ltd.