The ranges of N, Ne, Ar, Kr, and Xe ions in Be, B, C, and Al have been measured to ±10% for incident ion energy 50-500 kev. A monoenergetic ion beam from an electrostatic accelerator strikes a thick target of the absorber, and the penetration depth is determined by a momentum analysis of monoenergetic protons elastically scattered from the target and the embedded atoms. An expression relating the penetration depth to the actual path length is derived. A linear range-energy behavior is found for Ar, Kr, and Xe ions; for N and Ne ions $\frac{\mathrm{dE}}{\mathrm{dX}}$ increases with ion energy. The experimental ranges are 20% shorter than theoretical values based on energy loss by elastic nuclear collisions. By including electronic contributions to the stopping process, good agreement with experiment is achieved.

• Received 20 November 1961

DOI:https://doi.org/10.1103/PhysRev.126.61