MEASUREMENT OF L X-RAY-PRODUCTION CROSS-SECTIONS BY 400-700 KEV PROTON IMPACT ON RARE-EARTH ELEMENTS

The L-shell X-ray production cross sections of rare earth elements Dy, Ho, Er, Tm, Yb, and Lu by the impact of protons with energies between 400 and 700 keV have been measured. Thin films of the rare earth fluo rides have been employed as targets. A comparison with the predictions given by the ECPSSR theory of Brandt and Lapicki, following the algor tihm developed by Smit for their calculation, shows that this theory u nderestimates the measured cross sections. In order to obtain cross se ctions values which are more reliable, a compilation of most of the ex isting Lalpha line production cross sections (for elements with atomic numbers 45-92) was done. A scaling of the ratio of measured to ECPSSR values, with the reduced velocity parameter with relativistic correct ion xi(L)R, defined as xi(L)R = (xi(L1)R + xi(L2)R + 2xi(L3)R)/4, is t hen proposed and the results present a better agreement with the cross sections measured in this work. It is also found that more studies at low proton energies and heavy targets are required in order to check the validity of the ECPSSR theory for small values of xi(L)R.