L X-ray fluorescence cross sections in the atomic region 62  Z  70 excited by 15.20,17.80,23.62 and 24.68 keV photons

L x-ray fluorescence cross-sections were measured for the elements Sm, Ho and Yb using photon energies of 15.20, 17.80, 23.62 and 24.68 keV, Measurements were performed using an x-ray tube with a modified exciter system as the excitation source, In order to improve the efficiency of the detection system, the excitation source, the sample and the detector assembly were placed in a vacuum chamber and a pressure of 10(-2) mbar was maintained throughout the measurements, The present system considerably reduced the scattering and background effects and improved the monochromaticity, The x-ray transitions were chosen on the basis of experimentally observed spectra and a particular goup of x-rays are included in the calculation of fractional x-ray emission rates. The experimental results were in excellent agreement with theoretical values.