PRODUCTION OF M X-RAYS ON DECAY OF L(3) SUBSHELL VACANCIES TO M-SHELL IN PB, TH AND U

M shell x-ray production cross sections in thick targets of Pb, Th and U by K x-rays of Rb, Nb and Mo respectively have been measured. As the incident K x-ray energies are above the L(3) edge but below L(2) edge energies of the respective target elements under reference, the M x-rays are produced not only due to direct interaction of incident photons with M shell electrons but also due to the decay of L(3) subshell vacancies to M shell. The measured values have been compared with those calculated using known values of M and L(3) subshell photoionization cross sections and fluorescence yields etc, wherever possible. The percentage contribution due to shift of L(3) subshell vacancies to M shell to the total M shell x-ray emission were evaluated and it is seen that the shift contributes nearly 50% of the total M x-rays produced in the case of Pb while it is nearly 75% in the case of Th and U at the incident energies under reference.