Angular Distributions of Alpha-particles from F¹⁹, Al²⁷ and P³¹ bombarded with Protons

Abstract

The angular distributions of the alpha-particles were obtained for the reactions F¹⁹(p, α) O¹⁶ leaving the residual nucleus in the ground state, Al²⁷(p, α) Mg²⁴ and P³¹(p, α) Si²⁸ leaving the residual nuclei in the ground and first excited states at four bombarding energies between 6.0 MeV and 7.4 MeV. The angular distribution for the reaction F¹⁹(p, α) O¹⁶ shows the backward peak at each energy, but at small angles it depends on the bombarding energy. The angular distributions for the reactions Al²⁷(p, α) Mg²⁴ and P³¹(p, α) Si²⁸ are also energy-dependent, but contain a larger isotropic part than those for the reaction F¹⁹(p, α) O¹⁶. The integrated cross sections for the reactions Al²⁷(p, α) Mg²⁴ and P³¹(p, α) Si²⁸ leaving the residual nuclei in the first excited states are several times as large as those for the reactions leaving the residual nuclei in the ground states. It appears unlikely that these reactions can be accounted for by the formation of compound nucleus or by simple direct interaction. The possible mechanisms through which these reactions may take place are discussed.