Ratio of Atomic Stopping Power of Graphite and Diamond for 1.1-Mev Protons

Abstract

The theory describing energy loss of heavy charged particles in matter predicts that different physical or chemical forms of the same element will have slightly different stopping powers. Since two different forms of a pure element exhibit the same nuclear scattering cross section, it was possible to measure the relative atomic stopping power of graphic and diamond by observing the yields of backscattered protens from thick targets. The atomic stopping power of graphite was measured to be 1.0604 plus or minus 0.0090 times that of diamond (for 1.1- Mev protons). Using the theoretical density of graphite, a calculation based on this result and Brandt's version of stopping theory yields the result that the molecular polarizability of graphite is 4.9 times thnt of diamond. If this calculation is made using the measured density of graphite, this polarizability ratio is 1.5, in agreement with the theoretical value. (auth)