T.R. Saitoh

Structure of the doubly odd nucleus 180Ta: Description of 23 bands

Abstract The structure of the doubly-odd nucleus 180 Ta has been studied by γ – γ coincidence measurements with a DC beam at 52 and 57 MeV and time-correlated γ – γ coincidence measurements with a pulsed beam at 55 MeV via the 176 Yb( 11 B, α 3n) 180 Ta reaction. In all measurements, γ -rays were detected in coincidence with charged particles. In the time-correlated γ – γ coincidence measurements with a pulsed 11 B beam, three rotational bands and one octupole vibrational band have been identified above the I π =15 − T 1/2 =30 μ s isomer. The configuration of three bands built on 8 + states has been discussed by means of three-band mixing calculations. BCS calculations with blocking have been used in support of configuration assignment of four- and six-quasiparticle structures. Totally, 19 rotational bands, one β -, one γ - and two octupole-vibrational bands, plus one intrinsic state have been identified with two-, four- and six-quasiparticle configurations. The K values of these bands range from 0 to 19. The K-forbidden transition rates are discussed on the basis of mixing between states with widely different K-values. The BBCS calculations predict a K π =22 − isomer not identified experimentally in this nor in previous works. A search for specific intermediate states which could explain the transformation from K π =9 − to 1 + during the astrophysical s- and r- processes was negative.

Coexistence of triaxial and prolate shapes in 171Ir

Abstract Excited states in 171Ir have been observed for the first time. Gamma-rays were assigned to the nucleus by the recoil-decay tagging method. The ground-state band has a structure consistent with an h 11 2 proton coupled to a core of large triaxial deformation. At high spins, a bandcrossing occurs which is interpreted as a change in shape to a prolate deformation. Band-mixing calculations are performed for 171–175Ir. These show that shape-coexistence between triaxial and prolate states in these nuclei follows the same systematics found in their Pt and Os neighbours. The systematics are also compared with deformations calculated for 171–179Ir using the code “Ultimate Cranker”. Dipole bands were also observed, but tilted axis cranking calculations suggest that they are associated with a collective rotation.

Erratum to “Collective and intrinsic structures in 183W” [Nucl. Phys. A 660 (1999) 171–196]☆

The structure of 183W has been studied by employing the 176Yb(14C,α 3n) reaction at 68 MeV. Five previously known rotational structure with one-quasiparticle configurations have been extended to higher spin states, and five new rotational bands with three- and five-quasiparticle configurations and a γ-vibration of a one-quasiparticle structure have been newly identified. In the ν7/2-[503] and ν11/2+[615] rotational structures, a signal of an admixture of an octupole- vibrational structure has been observed in their in-band B(M1)/B(E2) ratios and gΚ factors. In the Κπ = 19-M rotational band, a Coriolis effect on the ν1/2-[510] neutron has been identified. In all, 17 Κ-forbidden transitions have been observed. Energies of intrinsic states below 4 MeV have been calculated based on the Blocked BCS theory, and they are used in support of the configuration assignments.

Collective and intrinsic structures in 183W

Abstract The structure of 183 W has been studied by employing the 176 Yb( 14 C, α 3n) reaction at 68 MeV. Five previously known rotational structure with one-quasiparticle configurations have been extended to higher spin states, and five new rotational bands with three- and five-quasiparticle configurations and a γ -vibration of a one-quasiparticle structure have been newly identified. In the ν 7/2 − [503] and ν 11/2 + [615] rotational structures, a signal of an admixture of an octupole-vibrational structure has been observed in their in-band B (M1)/ B (E2) ratios and g K factors. In the K π =19 − rotational band, a Coriolis effect on the ν 1/2 − [510] neutron has been identified. In all, 17 K -forbidden transitions have been observed. Energies of intrinsic states below 4 MeV have been calculated based on the Blocked BCS theory, and they are used in support of the configuration assignments.

Neutron excitations across the N=50 shell gap in 102In

The structure of In-102 has been investigated by in-beam gamma-spectroscopic methods. Knowledge on the excited states of this nucleus has significantly been extended. Three cascades of transitions were observed to exceed the spin-energy domain spanned by the pig(9/2)(-1)v(d(5/2),g(7/2))(3) configurations. The new high spin states at similar to 4 MeV excitation energy could be assigned to the pig(9/2)(-1)v(d(5/2), g(7/2))(2)h (11/2) configuration, while at least those at 4.733, 5.192 and 5.853 MeV most likely arise from the vg(9/2) --> vd(5/2), g(7/2) one-particle-one-hole excitation across the N = 50 shell closure.