A. T. Semple

Detailed spectroscopy of the normally deformed states in 132Ce

Abstract High-spin states have been studied in 132 Ce produced in the 100 Mo( 36 S,4nγ) reaction using the EUROGAM II spectrometer. The structure of the normally deformed states ( β 2 ∼ 0.2) has been investigated. Eight ΔI = 2 bands and three ΔI = 1 bands have been identified and the level scheme extended up to spin and parity (40 + ) at an excitation energy 19.79 MeV. The results are interpreted with the aid of Woods-Saxon cranking calculations, which suggest a variety of triaxial (γ) shapes in this nucleus stabilised by specific active quasiparticle orbitals.

Evidence for multiple band terminations in 102Pd

Abstract The level structure of 102 Pd has been investigated using data collected with the Eurogam 2 array. Several cascades of γ-rays have been established up to high spins. Termination of rotational bands has been observed at I π = 28 − and 32 + , and tentatively at I π = 38 + and 42 + . The nucleus 102 Pd is the first case where rotational bands built on valence space configurations are followed from spin close to zero up to termination and, at higher spins, a smooth rotational band which appears to terminate is built on core excited configurations.

High-spin study of 128Ce and systematics of quasiparticle pair alignment

Abstract High-spin states have been studied in 128 Ce, produced in the 100 Mo( 32 S,4n) reaction, using the Euroball γ -ray spectrometer. A quadruples analysis ( γ 4 ) of the data has extended several bands to high spin. Systematics of quasiparticle alignments in cerium isotopes and relevant isotonic chains are discussed and compared to Woods–Saxon cranking calculations.

Measurement of transition quadrupole moments of high-spin states in the N=74 isotones 133Pr, 132Ce and 131La

Abstract The Doppler-Shift Attenuation Method has been used to extract transition quadrupole moments of high-spin bands in the N=74 isotones 133 Pr, 132 Ce and 131 La, produced in the 37 Cl + 100 Mo reaction. The results appear to be configuration dependent and, for 133 Pr and 132 Ce, the involvement of Ω=1/2 νh 9/2 and νf 7/2 intruder orbitals appears to enhance the collectivity at high spin ( I>25 ℏ ).

Neutron orbitals above the N = 74 shell gap at large deformation: spectroscopy in the superdeformed minimum of 133Ce

Abstract High-spin states in 133 Ce were populated via the 116 Cd( 22 Ne,5n) reaction at 120 MeV. Analysis of these data has revealed three new superdeformed bands in 133 Ce, two of which have transitions which are identical to those observed in the yrast bands of 132 Ce and 136 Nd. These bands have been interpreted as signature partners of the [530] 1 2 − orbital coupled to the 132 Ce yrast superdeformed core. The third band is believed to be built upon a π5 4 ν6 3 configuration at high rotational frequency and to show the effects resulting from an alignment of a pair of f 7 2 neutrons at ℏgω ⋍ 0.7 MeV. It is tentatively suggested that the sharp rise in the dynamic moment of inertia of this band at low rotational frequency may result from an admixture of the π5 4 ν6 1 configuration.

Low-lying levels and high-spin band structures in 102Rh

Abstract Levels in 102 Rh have been populated in the reaction 70 Zn+ 36 S at 130 MeV. The level structure of 102 Rh has been investigated using the EUROGAM II array. Low-lying states and four high-spin bands have been identified. The configurations of low-lying levels and two-quasiparticle bands are interpreted in the frame of the interacting boson-fermion-fermion model. The four observed band structures are also compared with cranked shell model calculations using a modified oscillator potential.

Four independent decay properties in the super-deformed well of 143Eu☆

Abstract The flow of γ-transitions through the superdeformed minimum of 143Eu is investigated by studying the intensities of four different types of γ-rays of superdeformed origin, obtained with a variety of gating conditions. They can all be explained rather well by schematic simulation calculations assuming only well known statistical properties. Information on level density, competition between E1 and E2 strengths and rotational damping width in the SD well is obtained, yielding a rather complete picture of the feeding mechanism into different regions of the second minimum.

Shape coexistence in 138Sm and evidence for the rotational alignment of a pair of N=6 neutrons

The level scheme of 138Sm has been extended up to Ipi =(32+) using gamma -ray coincidence data collected with the Eurogam array. The 106Cd(35Cl,3p)138Sm fusion-evaporation reaction was used at a bombarding energy of 150 MeV. Several new bands have been observed and the known bands extended to higher spin. Band crossings and shape coexistence are discussed with the aid of Woods-Saxon cranking calculations (CMS and TRS). Evidence is presented for a neutron (i132/)2 pair alignment which is predicted to drive the nucleus to a prolate shape with enhanced quadrupole deformation beta 2=0.32. A strongly coupled band was also established and is interpreted as a collectively rotating oblate structure.

The role of shell gaps and deformation-driving orbitals in superdeformed

Four superdeformed bands have been assigned to following a high-statistics -ray study using the EUROGAM II spectrometer. The bands are interpreted in terms of and signature-partner neutron configurations. One of the bands exhibits a sharp backbend when the orbital crosses the orbital at MeV/ . Below this crossing, the band is predicted to remain superdeformed despite the absence of N = 6 neutron intruders. This suggests that these intruders are not a necessary ingredient of superdeformation in this mass region but that the underlying shell gaps at Z = 58 and N = 72 are important.

High-spin studies of neutron-deficient A=138 nuclei: 138Eu and 138Gd

The level schemes of mass A approximately 138 nuclei have been extended using data collected with the Eurogam array. The 35Cl+106Cd fusion-evaporation reaction was used at a bombarding energy of 150 MeV. Results are presented for odd-odd 138Eu and even-even 138Gd. The high-spin behaviour is discussed in terms of quasiparticle alignments of h11/2 proton and neutron pairs.