Saturation in the K-shell excitation of 120 MeV S14+ ions in interaction with gas targets

In contrast to the first Born approximation predicted quadratic enhancement, saturation has been observed in the excitation cross-sections of 120 MeV S14+ ions in interaction with gas targets. The measured cross-sections agree with the theoretical calculations in the framework of the Schwinger variational principle. The symmetric eikonal CDW approximation, however, underestimates the cross-sections with the heavier target atoms. (orig.)