Total electron-loss cross sections and absolute charge-state yields of 20-MeV Fe ions transmitted through gaseous targets

Absolute charge-state yields of 20-MeV Fe ions emerging within a large acceptance angle from a differentially pumped gas cell of length 9.4 cm have been measured using ${\mathrm{N}}_2$, Ar, Kr, Xe, and S${\mathrm{F}}_6$ targets. The gas pressures ranged from 2 to 400 mTorr, thereby including target thicknesses where single events dominate the charge change, as well as target thicknesses where charge-state equilibrium is established. From the low-pressure yields total cross sections, ${\sigma }_{4q}$ with $q=5-15\mathrm{}$ were obtained using an improved version of the initial growth method.