Energy straggling ofαparticles in solid materials

The energy straggling Ω² of 0.5-, 1.0-, 1.5-, and 2.0-MeV α 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 Ω² versus target thickness dependence and a mild increase with energy for a fixed target thickness. When Ω² is plotted as a function of Z₂, 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.