The L-3l, L-3 alpha, L-3 beta, L-2 beta, L-2 gamma, L-2 eta, L-1 beta and Li gamma 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 Co-57 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.