The angular distribution for the elastic scattering of 40-Mev alpha particles from C, Al, Ti, Cu, Nb, Mo, and Ag has been measured. The angular distributions are characterized by strong diffraction patterns in contrast to the monotonically decreasing angular distributions of alpha particles scattered from Ta, Au, Pb, and Th. An analysis of the relative positions of the diffraction maxima yields a value for the interaction radius of $\left[\right(1.27\mathrm{}\pm 0.07)A^{\frac{1}{3}}+(1.60\mathrm{}\pm 0.23\left)\right]\times {10}^{-13\mathrm{}}$ cm. A comparison is made of the angular distributions measured at the energies of 19, 22, 40, and 48 Mev.

• Received 30 November 1955

DOI:https://doi.org/10.1103/PhysRev.101.1508