L subshell ionization of heavy elements by 3He and 4He ions

L shell X-ray production cross sections for selected heavy elements (72≤Z2≤83) have been measured by 3He+ and 4He+ ions impact. The corresponding L subshell ionization cross sections have been extracted from data and compared with the predictions of the ECPSSR and SCA theories by expressing graphically the ratio σexp/σtheory as a function of the corrected reduced velocity parameter ξLir. Strong underestimation of experimental data by the ECPSSR and SCA theories has been observed for the lowest energies, especially for the L2 subshell, up to a factor of 3 and 4 for 3He and 4He ions, respectively. Possible reasons for observed disagreement are discussed. (orig.)