W. Gast

Excited states in124Xe

Excited states of124Xe have been investigated via the122Te(α, 2n),114Cd(13C, 3n) and108Pd(19F, p2n) reactions using in-beam gamma-ray and electron spectroscopy methods. 36 new levels and several spin and parity assignments were established, revealing the existence of at least one positive parity superband and two negative parity bands, one of them showing backbending.

Superdeformed band in 146Gd. First observation of band crossing

Abstract A discrete superdeformed band is found in 146 Gd. Lifetime measurements yield an average quadrupole moment of 12±2 e b. A band crossing corresponding to an alignment of ≈2ħ is observed at a rotational frequency of 0.65 MeV. A theoretical analysis suggests that the band has a π6 2 v7 1 configuration with odd spins and odd parity. Arguments are given that the [651 1/2] and [642 5/2] single-particle states are involved in the band crossing.

Prealignment B(E2)-anomaly in 124Xe

Lifetimes of 17 levels of 124Xe were measured using the Recoil Distance Doppler Shift method. An anomalous E2-reduction was observed, starting at Iπ = 8+ and Iπ = 5+ in the groundstate and in the quasi-gamma band respectively. This anomaly is discussed in terms of the Interacting Boson Model.

Excited states in 130Ba

Abstract Excited states of 130Ba have been studied by means of in-beam γ-ray spectroscopy and electron-spectroscopy via the reaction 120Sn(13C, 3n). Spin and parity assignments have been made for 28 new levels. A comparison with a cranking-model calculation shows that the negative-parity band based on the 5− state is a two-quasiproton band.

Study of the high-spin structure of 144Gd

Abstract High-spin states in 144 Gd have been investigated through the 108 Pd( 40 Ar, 4n) reaction. An extended level scheme is proposed. A ridge structure has been observed in a γγ coincidence matrix, consistent with energy spacings in the superdeformed bands of neighbouring nuclei. Several discrete high-spin sequences have been observed. They are interpreted in the context of cranked-Strutinsky-type calculations in terms of different coexisting shapes.

Spectroscopy of195Hg and196Hg

High-spin states in the oblate-deformed nuclei195Hg and196Hg were populated in the198Pt(α, xn) reaction and investigated by in-beamγ-ray spectroscopy using six Compton-suppressed Ge detectors. The level schemes of both nuclei are extended considerably. The level structure is interpreted within the framework of the cranked shell model. Good agreement is obtained between model predictions and experimental results.

In-beam spectroscopy of 120Xe☆

Abstract Excited states of 120 Xe have been studied by in-beam γ-ray spectroscopy using the 110 Cd( 13 C, 3n) and 111 Cd( 12 C, 3n) reactions. The yrast band was observed up to the 14 + level, showing backbending at the 12 + state. A γ-band and two new negative-parity bands were found. The low-lying levels of 120 Xe could be described by the IBA-1 hamiltonian plus a triaxial degree of freedom.

High spin states in73Se observed by the reaction70Ge(α,nγ)

Abstract73Se has been investigated by the reaction70Ge(α, nγ). Gamma excitation functions (Eα=10–16 MeV), gamma angular distributions (Eα=18 MeV) and gamma-gamma coincidences (Eα=15 MeV)) have been taken. A level scheme has been established, spins and partities have been assigned. States of a rotational band on the 151.2 keV (5/2−) state and an anomalous band have been identified.Nuclear Reaction70Ge(α,nγ)Eα=15 and 18 MeV; measuredEγ,Iγ,γ-γ-coin.,γ-angular distribution,γ-excitation function.73Se deduced levels,J, π. Enriched target, Ge(Li).

Development of composite Ge detectors for EUROBALL

Abstract The proposals of the EUROBALL Design Group for the development of large composite Ge detectors for an improved 4π detector array with a total full energy peak efficiency of p ph > 0.15 are presented. Cluster detectors are composed of hexagonal tapered coaxial Ge detectors while Stack detectors are composed of large diameter planar detectors. The status of the development is discussed and first experimental results of the properties of a hexagonal tapered Ge detector are presented.

79Se investigated by the reaction76Ge(α, nγ)

Abstract79Se has been investigated by the reaction76Ge(α, nγ). Gamma excitation functions (Eα=10−15 MeV), gamma angular distributions and gamma-gamma coincidences (both at (Eα=12 MeV), have been taken. A level scheme has been established, spins and partities have been assigned. The results are compared with rotational bands in neighbouring odd Se isotopes.Nuclear reaction76Ge(α, nγ)Eα=12 MeV; measuredEγ,Iγ,γ-γ coincidences,γ-angular distribution,γ-excitation function.79Se deduced levels,J, π. Enriched target, Ge(Li).