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Configuration-constrained potential-energy-surface calculations have been performed to investigate multiquasiparticle high-if states built on superdeformed minima in 192,194,196Pb and 198Po. The calculations predict that 196Pb and 198Po would be favorable candidates for the observation of low-lying superdeformed two- and four-quasiparticle high-K states. The possible decay paths and lifetimes that could lead to isomers are evaluated in detail for 196Pb. Comparisons between the predictions and previous observations of octupole-vibrational excitations indicate also that bands built on superdeformed high-K intrinsic states may compete with the octupole-vibrational mode in this mass region. The quadrupole moments of both the collective and intrinsic excitations are analyzed. [ABSTRACT FROM AUTHOR]

The partial conservation of the seniority symmetry in j = 9/2 shells has been discussed recently. In this work we show that the occurrence of the partial conservation of the seniority is the consequence of special properties of certain one-particle coefficients of fractional parentage. Further studies have also been done to pursue the similar special relations of the coefficients of fractional parentage in other single-;' shells with j ≲15/2. [ABSTRACT FROM AUTHOR]

We investigate the influence of deformation on the possible occurrence of long-lived K isomers in Hf isotopes around N = 116, using configuration-constrained calculations of potential-energy surfaces. Despite having reduced shape elongation, the multiquasiparticle states in 186,188Hf remain moderately robust against triaxial distortion, supporting the long expected occurrence of exceptionally long-lived isomers. The calculations are compared with available experimental data. [ABSTRACT FROM AUTHOR]

We have calculated the strength functions of the Gamow-Teller transition processes from mirror pairs 46Ti–46Cr and 50Cr–50Fe to the odd-odd N = Z nuclei 46V and 50Mn. The calculations are carried out in fp model space with shell model diagonalization method. Calculations are compared with experimental observations. We have also discussed the effects of isospin symmetry breaking on the analogous transitions. [ABSTRACT FROM AUTHOR]

High-spin states in 169Re were studied and resulted in the identification of a strongly coupled band based on the 9/2- [514] Nilsson state and a decoupled band built on the h9/2 1/2- [541] intruder proton orbit. The cranked-shell-model calculations present configuration-dependent deformations that can explain the different band crossing frequencies. The 9/2- [514] band in 169Re shows the largest signature splitting at low spin among the known odd-mass Re isotopes. After the alignment of a pair of i13/2 neutrons, the phase of the splitting is inverted with a significantly reduced amplitude. For the 9/2- [514] bands in light odd-A Re isotopes, the signature splitting of the Routhians and its relation with the signature dependence of M1 transition matrix elements are investigated in connection with the deviation of nuclear shape from axial symmetry, suggesting an appreciable negative γ deformation for the very neutron-deficient odd-A Re isotopes. Additionally, a three-quasipariticle band was observed and assigned to be built likely on the &pie;9/2-[514] ® AE configuration. [ABSTRACT FROM AUTHOR]

The very neutron-deficient nuclide 129Pm was produced via the 92Mo(40Ca, p2n) reaction and identified for the first time by using the X-γ coincidence in combination with a He jet tape transport system. According to the decay curve of a 99 keV γ-ray which corresponds to the known &frac52; → ½ transition in the daughter nucleus 129Nd of the 129Pm decay, the half-life of 129Pm was determined to be 2.4(9) s. Based on the nuclear potential energy surface (PES) calculations, the ground-state spin-parity of 129Pm was predicted as &frac52; which is favorable to feed a &frac52; low-lying state in the daughter nucleus 129Nd via the (EC 1β+) decay. [ABSTRACT FROM AUTHOR]

We present a basis selection method for truncated shell-model calculations. In this method, the correlated basis is constructed with the eigenvectors of the Hamiltonian that is diagonalized in each partition of the shell model. A truncation scheme is established by naturally taking the low-lying correlated-basis vectors in different partitions, which is equivalent to the j j -coupling scheme of the shell model when all the correlated-basis vectors are considered. The results are compared with standard shell-model calculations. The convergence properties of the correlated-basis method are discussed. [ABSTRACT FROM AUTHOR]

Using deformed Hartree-Fock and angular momentum projection (PHF) technique we try to understand the intrinsic structure and the systematics in the life times of K = 6+ isomers in the Hf isotopes (in 172-178Hf nuclei) and N = 104 Yb, Hf and W isotones. The band structure in 172Hf is reasonably well reproduced. The variation in the B(E2;2+ → 0+) values in the Hf isotopes as well as N = 104 isotones are well reproduced. The calculated K-forbidden E2 transition probabilities from the isomer bandheads to the 4+ yrast states qualitatively explain the variation of the lifetimes with N and Z. [ABSTRACT FROM AUTHOR]