The angular distributions of gamma rays following (α, n) and (p, n) reactions

The angular distribution of gamma rays excited by both (p, n) and (α, n) reactions leading to the final nuclei ⁵⁹Ni, ⁶³Zn and ⁶⁸Ga have been investigated. The observed angular distributions are consistent with those theoretically predicted by the compound nucleus statistical model whenever the spin sequence is previously known. The (p, n) and (α, n) reactions yield identical values of the multipole mixing ratios for all the transitions. The variation of the gamma-ray angular distributions with incident energy following the (p, n) reaction is correctly predicted by the model. The energies of the low-lying levels of ⁶⁸Ga have been accurately determined, and the first excited state at 175 keV excitation is found to have a spin 2⁽⁺⁾. The results indicate that the level at 375 keV is probably a doublet.