Production and deexcitation of highly excited 67Ga

The energy spectra and angular distributions of alpha particles and protons emitted from 67Ga compound nuclei at excitation energies of 110 to 116 MeV formed in four different reactions have been measured. The populated angular momentum ranges deduced from fusion cross section information correspond to 0–24 ħ for 4Cu, 0–38 ħ for 12Mn, 0–48 ħ for 16V, and 0–50 ħ for 40Al. The experimental data are analyzed using the angular-momentum-dependent statistical model and the rotating liquid drop model. Average multiplicities and barriers are extracted for different zones of angular momentum. Comparisons with the models indicate large deformations of the 67Ga nuclei at the higher angular momenta and suggest large deformation related increases in the nuclear level density and decreases of emission barriers. The p/α ratio decreases with increasing angular momentum less than expected for spherical emitters at the higher angular momenta. The average α emission barriers are found to be close to those which are calculated for emission from the tips of prolate deformed nuclei such as those predicted by the liquid drop model. The experimental proton barriers appear somewhat smaller than those calculated using the liquid drop model shapes.