Search

A first level scheme of ${}^{68}\mathrm{Se}$ with five states up to 4.2 MeV excitation energy and tentative spins ${6}^{+}$ and ${7}^{\ensuremath{-}}$ has been established from \ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\gamma} coincidences measured with six EUROBALL Cluster detectors in close geometry. The level scheme is interpreted in comparison with neutron deficient nuclei of the $A\ensuremath{\approx}70$ region and cranking model calculations. In a similar experiment a triple coincidence between the ${}^{72}\mathrm{Kr}$ transitions 710, 611, and 792 keV has been proven.

The high-spin states of 147Tb have been studied with regard to their spins. The data were obtained by in-beam γ-ray spectroscopy using the reaction 120Sn(31P,4n)147Tb at 152 MeV performed at the Osiris spectrometer in Berlin. We obtained multipole mixing ratios for 60 transitions, and level spins up to 67/2ħ are introduced.

Superdeformation in {sup 146}Gd has been studied using the EUROGAM I spectrometer at the NSF Daresbury. The two known superdeformed (SD) bands in {sup 146}Gd have been extended to 15 transitions. All transitions within each band were clearly observed in coincidence among each other and accurate {gamma}-ray energies were determined. The association of both bands to {sup 146}Gd has been unambiguously confirmed. In addition a band with energies corresponding to the first known SD band in {sup 147}Gd was also observed. Several methods to search for new SD bands were applied.

A discrete superdeformed rotational band has been discovered in [sup 144]Gd following the reaction [sup 100]Mo([sup 48]Ti, 4[ital n])[sup 144]Gd at 221 MeV. The dynamical moment of inertia shows a sharp irregularity at [h bar][omega]=0.45 MeV. The intensity of the [gamma]-ray transitions suggests that the irregularity can be associated with a backbend, which is interpreted in terms of the [ital N]=6 proton band crossing. The experimental results are in good agreement with cranked mean field calculations, which indicate the presence of large shell gaps for both protons and neutrons.

Lifetimes of two superdeformed states in 192Hg were measured with the recoil distance Doppler shift coincidence method, using the 160Gd(36S,4n)192Hg reaction at a beam energy of 168 MeV. The experiment was performed with the GASP set-up at the LNL, Legnaro. The obtained transitional quadrupole moments are in accordance with those obtained previously for the higher members of the superdeformed band.

The level scheme of147Tb has been extended to 116 levels and 198 transitions in two experiments with the OSIRIS Compton suppressed detector array at the HMI Berlin with the reactions122Sn(31P, 6n)147Tb at 160 MeV and120Sn(31P, 4n)147Tb at 152 MeV. Evidence for a new high spin isomer atE=7664.1 keV with a life-time of the order of 2 ns has been found.

Picosecond lifetimes in ${}^{129,130}\mathrm{Ba}$ were determined using the recoil distance technique with a plunger device coupled to an array of EUROBALL-cluster-detectors for the first time. The differential decay curve method in coincidence mode was employed to derive lifetimes for six states in ${}^{129}\mathrm{Ba}$ and twelve states in ${}^{130}\mathrm{Ba}.$ The resulting $B(E2)$ values are compared with triaxial rotor plus particle calculations for ${}^{129}\mathrm{Ba}$ and, in ${}^{130}\mathrm{Ba},$ to the predictions of the general collective model, the interacting boson model, as well as to the symmetric and asymmetric rotor models. In ${}^{130}\mathrm{Ba},$ the transitional quadrupole moment in the ground state band is remarkably constant before and after the backbend. With this data the two-quasiparticle negative parity band in ${}^{130}\mathrm{Ba}$ was confirmed to be based on a $\ensuremath{\pi}{(h}_{11/2}\ensuremath{\bigotimes}{d}_{5/2}{/g}_{7/2})$ configuration.

High-spin states in ${}^{124}\mathrm{Xe}$ were populated in the fusion-evaporation reaction ${}^{110}\mathrm{Pd}{(}^{18}\mathrm{O}{,4n)}^{124}\mathrm{Xe}$ at a beam energy of 86 MeV. The experiment was performed at the NORDBALL spectrometer in Ris\o{}, Denmark. The decay out of a magnetic dipole band was established for the first time in this nucleus. By means of angular correlations from oriented states the multipole mixing ratios for 9 of the 12 gamma transitions of the magnetic dipole band were deduced. The experimental $B(M1;\stackrel{\ensuremath{\rightarrow}}{I}I\ensuremath{-}1)/B(E2;\stackrel{\ensuremath{\rightarrow}}{I}I\ensuremath{-}2)$ values were compared to estimates of the D\"onau-Frauendorf semiclassical model. The dipole band is inferred to be based on a prolate four-quasiparticle configuration of the type $[\ensuremath{\nu}{(h}_{11/2}\ensuremath{\bigotimes}{g}_{7/2})]\ensuremath{\bigotimes}[\ensuremath{\pi}{(h}_{11/2}\ensuremath{\bigotimes}{d}_{5/2}{/g}_{7/2})].$

A new high-spin isomer in 145Sm was observed by in-beam γ-ray spectroscopy with the reaction 122Sn(27Al,3np) at 127 MeV performed at the Nordball multi-detector array in Roskilde. The excitation energy of the isomer was determined to be Ex= 11147 keV, and using the generalized centroid-shift method its half-life was found to be T1/2= (7.4 ± 1.0) ns.

The data from two experiments with heavy ion induced reactions at the OSIRIS Compton suppressed Ge detector array has been analyzed to study high spin states in145Gd. The level scheme of145Gd has been extended up to an excitation energy of 12 MeV and an estimated spin of 25 ħ. No evidence for high spin isomers was found.

Excited states of the nuclei127Xe and125Xe have been investigated in the inverse kinematic reactions48Ca(82Se,(3.5)n) at 275 MeV beam energy with the OSIRIS multidetector system at the VICKSI-accelerator of the HMI Berlin. The level scheme of127Xe was extended up to a level of tentative spin (51/2−). Two excited bands of 3QP-character were observed. For125Xe these structures were extended towards higher spins. Experimental Routhians of selected bands are presented.