EN
The L_{3l}, L_{3α}, L_{3β}, L_{2β}, L_{2γ}, L_{2η}, L_{1β} and L_{1γ} X-ray production cross-sections and L shell average fluorescence yields were measured for the elements from Re to U using excitation energy of 123.6 keV. Measurements were performed using an ^{57}Co annular radioactive source and a Si(Li) detector. The theoretical values of the cross-sections were calculated using theoretically tabulated values of subshell photoionization cross-sections;the Coster-Kronig transition probabilities were based on the Dirac-Hartree-Slater theory and radiative emission rates. Experimental results were compared with the theoretically calculated values of L shell X-ray cross-sections. The present experimental results are in agreement with theoretical values.