Level structures at high spins in nuclei at and near n=52

Theoretical calculations have indicated several interesting possibilities such as superdeformed structures, collective excitations and band terminations in the mass region A ∼90-100. High spin states in several nuclei in this region were populated using a 140 MeV 32S beam on a 65Cu target. Triple-γ coincidences were measured using the GAMMASPHERE facility. Several new transitions in 94,95Mo, 94,95Tc, 96,97,98Ru and 98Rh have been identified. The N = 51, 52 isotones in these nuclei (94Mo, Tc and 96Ru) exhibit a γ ray with energy of about 2 MeV. Such a transition is a signature of the N = 50 core excitation. Preliminary investigations of the level structures for the N = 53, 54 isotones suggest a collective behaviour. Level schemes of these nuclei will be presented, and discussed within the framework of spherical shell model calculations