L-SUBSHELL IONIZATION OF RARE-EARTH ELEMENTS BY CARBON ION-BOMBARDMENT

Measurements of L-shell x-ray production cross sections and corresponding L-subshell ionization cross sections for selected rare earth elements (57 less-than-or-equal-to Z less-than-or-equal-to 68) have been performed for C-12 and C-13 ion impact with energies 0.4-2.8 MeV amu-1. The influence of target thickness and projectile charge state on L-subshell ionization is examined experimentally. The measured L-subshell ionization cross sections are compared with the predictions of the ECPSSR and SCA theories. Strong underestimation of the experimental data in the low energy range by both theories is caused by the second-order effects not accounted for in the theoretical description, An agreement of the data with the theoretical predictions is improved by using the 'united atom' limit for the effective binding energies.