The Stopping Power of Metals and Semiconductors

Stopping power measurements have been made on Si, Ni, Cu, Ge, Zr, Rh, Ag, Sn, and Au. The reduction in range of the cyclotron deuteron beam produced by samples of these materials was determined by measurement of the ionization in air at the end of the beam path. To evaluate the ionization curves a semi-empirical curve, given here, which relates extrapolated ranges with mean number ranges was computed for large straggling parameters. A range-energy curve for deuterons in Ge is given as well as approximate air and Al equivalents for Si and Ge. Range-energy curves were measured for the metals.The semiconductor results were compared with those for the metals to determine whether the difference in electrical properties produces a difference in energy loss. No difference was detected within the limits of precision of this experiment.Combining data from this experiment with those of other investigations a study of the dependence of stopping power on velocity and atomic number has been made. An empirical formula derived from these data expresses the electronic stopping power relative to Al as a function of energy and atomic number over a wide range. A formula is provided for using this relation to calculate range-energy curves in any element with $Z>10$, and its validity is discussed.