Energy straggling ofαparticles in solid materials

Abstract

The energy straggling ${\Omega }^2$ of 0.5-, 1.0-, 1.5-, and 2.0-MeV $\alpha$ particles in thin vapor-deposited films of Ti, Cr, Co, Cu, and Ag onto a thick substrate has been measured to ±6% by an elastic scattering technique using a magnetic spectrometer. The measurements reveal a linear ${\Omega }^2$ versus target thickness dependence and a mild increase with energy for a fixed target thickness. When ${\Omega }^2$ is plotted as a function of $Z_2$, a decrease in energy straggling with increasing atomic number is observed, although it is considerably higher than predicted by the Bonderup-Hvelplund modification of the Lindhard statistical approach.