Influence of a critical angular momentum on angular distributions of spin-zero particle reactions

Recently, groups at Yale and Saclay have shown evidence for an angular-momentum upper limit at a given excitation energy of the compound nucleus by comparing experimental absolute cross-sections with Hauser-Feshbach calculations. An alternative method to study these high-spin limits can be used by analysing angular-distribution shapes; indeed, when both incoming and outgoing particles have zero spins, angular distributions show strongly oscillating patterns which are characteristic of high-spin states in the intermediate compound nucleus. To illustrate this method, some data of the 12C(12C,α)20Nesub(g.s.) reaction are discussed. (Auth.)