Threshold Effects in Proton-induced Reactions on Copper

Abstract

A study has been made of proton-induced reactions on the two copper isotopes 65CU and 63CU for bombarding energies in the range 1·2-4·6 MeV. This energy range includes the (p,n) thresholds for 65CU and 63CU, which occur at 2·17MeV and 4·21 MeV respectively. Excitation functions for (p, y) reactions were obtained by observing discrete y-ray transitions between low-lying states of the compound nuclei. Data were also obtained for the charged-particle reactions 65Cu(p,lXo)62Ni and 63CU(p, lXo.,)6°Ni. As the respective (p, n) thresholds are crossed, the yields of proton-induced reactions on 65CU fall by a factor of about 5 while the excitation functions of proton-induced reactions on 63CU reveal no evidence of a significant threshold effect. These data are ompared with Hauser-Feshbach statistical model calculations. The structure in the 65CU+p reaction yield is interpreted in terms of Wigner cusps.