The L-shell X-rays of Si, induced by 50-250 keV proton and 1.0-3.0 MeV Ar 11+ ions impacting are measured. It is found that the X-ray induced by Ar 11+ is about 36 eV higher than that induced by proton. That indicates that 3, 4 L-shell electrons of Si atom are multiply-ionized by Ar 11+ ion impact. The X-ray production cross section is extracted from the yield data and compared with the results from the BEA, PWBA and ECPSSR models. With the same unit incident energy, the cross section induced

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... Ar 11+ is about 3 orders of magnitude larger than that produced by proton. For proton impact, the ECPSSR model gives an accurate prediction to the cross section data. However, the BEA model, considering the change of fluorescence yield due to the multiple-ionization, presents the results that are in better agreement with the experimental results for Ar 11+ ions.