L-Shell Ionization Cross Sections of BA, CE, ND, SM and DY for Proton Energies from 0.5 to 2.0 MeV

Protons from the University of Texas at Arlington´s 2 MV Van de Graaff accelerator were used to produce characteristic L x-rays from thin targets of Ba, Ce, Nd, Sm and Dy. Incident proton energies were varied from 0.5 to 2.0 MeV. The x-rays were detected by an ORTEC High Purity Germanium Low Energy Photon Spectrometer (LEPS) mounted at 90° to the beam direction. The incident proton beam was monitored by a particle detector also mounted at 90° to the beam direction. The measured x-ray production cross sections were converted to ionization cross sections by the use of subshell fluorescence yields and Coster-Kronig transition probabilities taken from Bambynek. Comparison of these ionization cross sections as well as the ratios of selected subshell x-ray yields with the predictions of the Plane Wave Born Approximation (PWBA) and the Binary Encounter Approximation (BEA) show that the PWBA predictions fit the experimental results much better than the BEA predictions.