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Multiple-particle, y~ray coincidence techniques have been used to study neutron-deficient isotopes near N -Z -40. Results are presented for 77~80 Sr. Levels in 78 Sr were seen to J = 10 with E(2 + ) = 278 keV and T 1/2 = 155± 19 ps. The results suggest that this region contains some of the most deformed nuclei known, with quadrupole deformations e 2 ~ 0.4. These data resolve conflicting theoretical predictions of nuclear shapes and emphasize the important contribution of hexadecapole deformation in determining the most stable shape.

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The excitation function for the fusion-evaporation reaction 64 Ni + 100 Mo has been measured down to a cross section of ∼5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep falloff of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at E s = 120.6 MeV, which corresponds to 90% of the reference energy E ref s , a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactions leading to compound nuclei with mass A = 100-200 is presented in order to explore a possible dependence of fusion hindrance on nuclear structure.