Stopping of Dysprosium Ions in Gases and Aluminum

The stopping of Dy recoils of 6 to 21 MeV in ${\mathrm{D}}_2$, He, ${\mathrm{N}}_2$, Ne, Ar, Kr, and Xe has been studied by electrostatic collection. The range-energy data (along with previous results for Al and ${\mathrm{H}}_2$) are compared with stopping theory. Range straggling due to the stopping process has been measured for the heavier gases. The magnitude of the electronic stopping has been estimated from range data, and independently from straggling data. These estimates suggest that electronic stopping cannot be adequately approximated as being proportional to velocity.