Nuclear Fission and Structure Studies with Gammasphere

Abstract

The γ-rays emitted in the spontaneous fission of ²⁵²Cf has been studied with Gammasphere. The yields of correlated Mo-Ba pairs in binary fission with 0–10 neutron emission have been remesured with an uncompressed cube. The previous hot fission mode with 8–10 neutron emission seen in the Mo-B a split is found to be smaller than earlier results but still present. New 0n binary SF yields are reported. By gating on the light charged particles detected with ΔE-E detectors mounted inside the Gammasphere chamber and γ — γ coincidences with Gammasphere, the relative yields of correlated pairs in alpha ternary fission with zero to 6n emission are observed for the first time. Half-lives (T_1/2) of 7 states which decay by delayed γ transitions were determined from γ — γ — γ coincidences. High spin states in neutron-rich ^104,106Mo nuclei have been investigated. The known ground state band, one-phonon and two-phonon γ-vibrational bands and two-quasiparticle bands are extended to high-spin. The one- and two-phonon γ-bands have remarkably close in energies. Several new quasiparticle bands are observed in both nuclei. In addition to their triaxial shape and large deformation, both high j two quasi-proton and two quasi-neutron orbitals close to the Fermi surface provide the necessary conditions for chiral bands. Two pairs of bands in ¹⁰⁶Mo are found to have all the characteristics of chiral doublets, the first such in an even-even nucleus.