K shell ionization cross sections of Au, Pb and Bi induced by low energy proton impact

Abstract

K X-ray production cross sections induced by proton impact were measured on thick targets of Au, Pb and Bi in the energy range 0.5 < E 0 < 1.7 MeV. The yields of characteristic X-rays were normalised to the yields of backscattered protons. For proton energies E 0 > 0.8 MeV, the deduced K shell ionization cross sections are uncertain by 12%, these uncertainties being smaller than those of the data published before. Our experimental results are compared with the semiclassical cross sections calculated within the united atom binding procedure. Experimental values agree well with theoretical ones, their difference being generally smaller than our experimental errors. The ionization cross sections measured for E 0 < 0.8 MeV are too large to be explained by proton induced direct ionization. We showed that for thick targets and proton energies smaller than E 0 < 0.8 MeV, the K-shell ionization is produced notably by fluorescence on account of bremsstrahlung photons emitted in the collisions between protons and target nuclei.