Scattering of 43-MevαParticles by Nuclei

The differential scattering cross sections for the elastic scattering of 43-Mev $\alpha$ particles by Zn, Ag, Rh, and Au are obtained over the angular range from 12° to 55°. The absolute errors in the cross sections are estimated to be less than 2% over most of the angular range. The group structure in the inelastic spectrum observed with protons and deuterons is also observed with $\alpha$ particles. In the spectra of Ag, Rh, and Zn, one group near 2.7 Mev was observed. In Al, V, and Ni a number of groups were observed. In Au and Ta no groups could be resolved. Angular distributions were obtained for the 2.5-Mev group in Rh and Ag and the 2.8-Mev group in Zn. In the case of the 2.8-Mev group in Zn, the angular distribution shows a very marked diffraction pattern. The data were fitted with Butler's theoretical expression modified to eliminate the assumption that the scattering of 43-Mev $\alpha$ particles by nucleons is isotropic in the center-of-mass system. It is shown that this assumption can be easily eliminated in the formal treatment. A comparison with the angular distributions obtained for the 1.04-Mev $2^{+}$ level in Zn with both 43-Mev $\alpha$ particles and 21.6-Mev deuterons indicates that $l=3\mathrm{}$ is the most plausible assignment for the 2.8-Mev group.