Search

Level schemes for the neutron-rich 140,143Ba nuclei have been determined by study of prompt γ-rays in spontaneous fission of 252Cf. The level pattern and enhanced E1 transitions between π = + and π = - bands show reflection asymmetric shapes with simplex quantum number s = +1 in 140Ba and s = ±i in 143Ba, respectively. The octupole deformation stability with spin variation has been discussed.

With prompt \ensuremath{\gamma}-ray and x-ray spectroscopy on fission fragments, several new transitions in $^{109,111}\mathrm{Ru}$ have been identified. Angular correlation analysis of several of the new transitions yield evidence of a stretched E2 band structure. Qualitative Nilsson model arguments, systematics, and triaxial rotor+particle calculations support our hypothesis that the observed band is built on the unique parity \ensuremath{\nu}${\mathit{h}}_{11/2}$ orbital.

New, high spin band structures are established for the neutron-rich nuclei 142,143,145,147Ba, and 144Ce, and levels of 144,146Ba extended to higher spins from the study of γ-γ and γ-γ-γ coincidence studies in spontaneous fission. Alternating parity sequences connected by strong electric dipole transitions are identified in 142,143Ba and 144Ce but not in 145,147Ba to confirm theoretical predictions of stable octupole deformation for N = 86.

The levels in neutron-rich odd-A 107,109Ru nuclei have been investigated by using γ-γ- and γ-γ-γ-coincidence studies of the prompt γ-rays from the spontaneous fission of 252Cf. The ground state bands and the negative parity bands are identified and expanded in both nuclei. Triaxial rotor plus particle model calculations indicate the ground state bands originate from ν(d5/2 + g7/2) quasiparticle configurations and the negative parity bands are from νh11/2 orbital.

The data of Independent yields of secondary fission fragment pairs (emerging after prompt neutron emission from primary fragment pairs) obtained by detecting coincidences between γ rays following the spontaneous fission of 252Cf have been expanded. Our approach to estimate characteristics of the primary fragments pairs (mass and excitation energy distributions) by unfolding the yields of secondary fragment pairs is discussed. Mew model parameters were introduced and results are presented here. The new results confirmed our old assumption that in case of Mo-Ba charge split the two fission modes differing with average total kinetic energy 〈TKE〉 on ∼36 MeV are realized.