Stopping power and straggling of 65–500 keV lithium ions in H 2, He, CO 2, N 2, O 2, Ne, Ar, Kr and Xe

Abstract

Stopping power and straggling of lithium ions with velocities around the Bohr velocity (65–500 keV) have been measured for a number of simple gases (H 2, He, CO 2, N 2, O 2, Ne, Ar, Kr and Xe). In contrast to the results of recent extensive measurements in solids by the inverted Doppler-shift method, the measured stopping powers are not strictly proportional to velocity, and for all targets d E/d x increases significantly faster than E 0.5. At the Bohr velocity, the measured stopping powers do not agree much better with results of semiempirical calculations based on Hartree-Fock-Slater wavefunctions than with the simple Lindhard-Scharff formula. For lighter gases, the straggling data are in approximate quantitative agreement with Hvelplund's calculations based on Firsov's differential energy-loss formula.