L X-ray fluorescence cross-sections of heavy elements excited by 16.04, 16.90 and 17.78 keV photons

Abstract

Abstract L l , L α , L β , L γ X-ray fluorescence cross sections have been measured for the elements Au, Pt, W, Lu, Yb, Tm, Ho, Dy and Tb using photon energies of 16.04, 16.90 and 17.78 keV. Measurements have been performed using an X-ray tube with a secondary-exciter system as an excitation source. The secondary exciters used are Zr, Nb and Mo of pure metal sheets (99.99%). A Mo X-ray tube with a secondary-target arrangement was used to obtain high intensity with a high degree of monochromaticity. Using an X-ray tube made it possible to measure X-ray fluorescence cross-sections and intensity ratios even for low intensity X-ray lines. The experimental values of the cross-sections were determined by measuring the absolute yield of L subshell X-rays emitted from a standard target of a given element irradiated with photons of given energy. The theoretical values of the cross-sections were calculated using theoretically tabulated values of subshell photoionization cross-sections, fluorescence yields, Coster–Kronig transition probabilities and radiative decay rates. Experimental results have been compared with the theoretically calculated values of L X-ray cross-sections. A fairly good agreement is observed between the experimental and the calculated values. The intensity ratios I Lβ / I Lα and I Lγ / I Lα were measured and found to be in good agreement with the calculated values.