Elastic Scattering of Heavy Ions by Gold and Bismuth

Abstract

The angular distributions of ${\mathrm{C}}^{12}$, ${\mathrm{N}}^{14}$, ${\mathrm{O}}^{16}$, and ${\mathrm{Ne}}^{20}$ elastically scattered by ${\mathrm{Au}}^{197}$ and ${\mathrm{Bi}}^{209}$ have been measured at laboratory energies of approximately 10.4 Mev per nucleon. The elastically scattered ions were recorded in photographic emulsions at laboratory angles from 19° to 175°. In general, measurements were extended only to angles where the ratio of the cross section to the Coulomb cross section, $\frac{\sigma }{{\sigma }_c}$, was greater than 0.1. In one case the measurement was extended to a region where $\frac{\sigma }{{\sigma }_c}\le 1.4\times {10}^{-4\mathrm{}}$. The cross sections all exhibited a behavior similar to that previously reported for ${\mathrm{C}}^{12}$ on ${\mathrm{Au}}^{197}$. An oscillation in the cross-section ratio occurring at smaller angles than the 20% to 30% rise and sudden drop was observed. Excellent agreement was obtained with the Blair "sharp-cutoff" calculations for values of $\frac{\sigma }{{\sigma }_c}>0.2\mathrm{}$. Nuclear interaction distances calculated by fitting the sharp-cutoff calculations are consistent with $r_0=1.46\mathrm{}$ fermis, where $R=r_0({A_1}^{\frac{1}{3}}+{A_2}^{\frac{1}{3}})$. No striking distinction can be made regarding the surface characteristics of the four projectiles or the two targets.