On the Angular Distribution in the ReactionF19(p,α)

Abstract

The angular distribution of the long range $\alpha$-particles shows marked lack of spherical symmetry, with asymmetry in the forward and backward directions. The distribution is constant with bombarding energy in the range 330 to 435 kev and contains large $cos\theta$ and ${cos}^2\theta$ terms with somewhat smaller and less certain amounts of the third and fourth powers. It is shown that the energy dependence implies broad levels and constant penetrabilities; the latter is found to agree with calculation. The experimental distributions can most simply be accounted for by the assumption that the chief contributions are from three levels of total angular momentum $J=0,1,2\mathrm{}$. This leads to the experimental curves without arbitrary assumptions as to the values of the line breadths or detailed assumptions about the nuclear coupling scheme. Powers of $cos\theta$ higher than the fourth in the angular distribution are not to be expected.