Slowing down of fast heavy ions in matter

Some characteristic features are presented on the stopping power. (S) and the energy loss straggling (delta E) of 0.5 to 10 MeV/u heavy ions (18 less than or equal to Z1 less than or equal to 92) in solids and gases. For partially stripped ions the stopping was found to be smaller in gases than in solids, suggesting that the ionic charge during the interactions is smaller in gases due to the lower collision frequencies. The Z2 oscillations decrease with increasing velocity and decreasing atomic number of the projectile. These experimental observations cause serious limitations in the accuracy of the effective charge concept which calculates the heavy ion stopping powers from those of protons. The effective charge is a function of the stopping medium and can vary by up to 20%. A comparison of effective charges in gases with the measured mean charge states after the medium indicates the influence of higher-order corrections. Comparisons with theories and semi-empirical tables demonstrate discrepancies in S values by up to 30%. The measured energy loss straggling of heavy ions in gases agrees surprisingly well with the simple Hvelplund-Firsov formula which does not include charge exchange straggling