High-spin states in Ho-160,Ho-161,Ho-162 have been populated in the reactions Gd-158,Gd-160(Li-7, xn) at 56 MeV. In all three isotopes the known rotational bands have been extended to significantly higher spin. In Ho-160, the band crossing in the pi7/2(-)[523] circle times v11/2(-)[505] band has been observed for the first time. The sequences built on the proton 7/2(-)[523], 7/2 (+) [404], 1/2 (+) [411] and 1/2(-)[541] states in Ho-161 have been extended up to spin 51/2(-), 35/2 (+) , 51/2 (+) and 41/2(-), respectively, leading to the first observation of upbends in all four cases. In addition, a new band most probably belonging to this nucleus has been identified. In the most neutron-rich isotope Ho-162, the only known rotational band, which is built on the pi7/2(-)[523] circle times v5/2(+) [642] configuration, has been extended up to the 28(-) state. The properties of all observed bands are discussed and compared to the neighbouring isotopes.

. High-spin states in 160,161,162 Ho have been populated in the reactions 158,160 Gd( 7 Li, x n) at 56 MeV. In all three isotopes the known rotational bands have been extended to significantly higher spin. In 160 Ho , the band crossing in the π 7/2 - [523] ⊗ ν 11/2 - [505] band has been observed for the first time. The sequences built on the proton 7/2 - [523], 7/2 + [404], 1/2 + [411] and 1/2 - [541] states in 161 Ho have been extended up to spin 51/2 - , 35/2 + , 51/2 + and 41/2 - , respectively, leading to the first observation of upbends in all four cases. In addition, a new band most probably belonging to this nucleus has been identified. In the most neutron-rich isotope 162 Ho, the only known rotational band, which is built on the π 7/2 - [523] ⊗ ν 5/2 + [642] configuration, has been extended up to the 28 - state. The properties of all observed bands are discussed and compared to the neighbouring isotopes.

High-spin states of the neutron-rich odd nuclei Dy-159,Dy-161,Dy-163 have been studied using the incomplete fusion reactions Gd-158,Gd-160(Li-7,(p,d,t)xn). In Dy-159, the band crossing in the 11/2(-)[505] band has been observed for the first time. Moreover, 11 E1 transitions connecting both signatures of the 3/2(-)[521] band to the 5/2(+)[642] band have been observed in this nucleus; the deduced B(E1)/B(E2) ratios as well as the B(M1)/B(E2) ratios for transitions within the 3/2(-)[521] band show a pronounced signature dependence. In Dy-161 and Dy-163, rotational bands have been extended to significantly higher spin values. In Dy-161, the sequences built on the neutron 5/2(-)[523] and 3/2(-)[521] states have been followed up to spin 49/2(-) and 33/2(-), respectively, and in both cases upbends have been observed around (h) over bar omegaapproximate to0.26 MeV. In addition, a new band most probably built on the 11/2(-)[505] single-particle state has been identified in this isotope. In Dy-163, both the 5/2(-)[523] ground state band and the structure built on the 5/2(+)[642] neutron orbit have been extended up to the 45/2(-) and 49/2(+) states, respectively. However, no band crossing has been observed in this nucleus. The properties of the observed bands in Dy-159,Dy-161,Dy-163 are discussed and compared to calculations performed within the projected shell model.

Progress in the experimental techniques used to investigate superdeformed fission isomers in the actinides allowed for detailed spectroscopic results of collective properties as well as for the identification of the rotational structure of multiphonon vibrational excitations. A novel approach could be established to determine the depth of the second potential well.

Excited states of the nucleus Br-79 were investigated via the reaction Ge-76(Li-7,4n) at a beam energy of 35 MeV. Coincidence data of emitted gamma rays were measured with an arrangement of six EUROBALL CLUSTER detectors. The E2 bands built on the 9/2(+) and 3/2(-) states were extended up to J=37/2 at Eapproximate to8.8 MeV. The M1 band starting with a 15/2(-) state at 2.6 MeV was observed up to J=(29/2) at E=6.4 MeV. Crossover E2 transitions within this band were observed for the first time. Mean lifetimes of 17 levels were deduced using the Doppler-shift-attenuation method. The M1 band can be described within the tilted-axis-cranking model on the basis of the tilted three-quasiparticle configuration pi(g(9/2)) nu(g(9/2)) nu(fp) which has a triaxial shape. This band appears as a mixed case including contributions of both magnetic and collective rotation.

The incomplete fusion reactions 7Li→158,160Gd at beam energies of 8 MeV/nucleon have been used to study the first band crossing region in the heavy stable Dy isotopes Dy. Theg rays were detected in the GASP spectrometer in coincidence with fast charged particles detected in the ISIS silicon ball. We succeeded to observe the first backbending in Dy at a crossing frequency of \v'350 keV, a value much higher than expected from other nuclei in this mass region. Moreover, for the first time in a nucleus with a very large interaction strength, the yrare band in Dy could be established up to rather high spin ( I 520\) allowing for a precise determination of the interaction strength between the ground state and the Stockholm band, uVg-Su 5219(2) keV. Together withuVg-Su514(2) keV determined for the corresponding interaction in Dy, a full oscillation of the strengths from one node to the next could be observed within an isotopic chain. In addition to the ground state and Stockholm bands, many other known bands in the two nuclei were considerably extended to higher spin and the experimental results are compared to calculations within the projected shell model.

As a tool for studying the structure of nuclei far off stability the technique of γ-ray spectroscopy after low-energy single-nucleon transfer reactions with radioactive nuclear beams in inverse kinematics was investigated. Modules of the MINIBALL germanium array and a thin position-sensitive parallel plate avalanche counter (PPAC) to be employed in future experiments at REX-ISOLDE were used in a test experiment performed with a stable 36S beam on deuteron and 9Be targets. It is demonstrated that the Doppler broadening of γ lines detected by the MINIBALL modules is considerably reduced by exploiting their segmentation, and that for beam intensities up to 106 particles/s the PPAC positioned around zero degrees with respect to the beam axis allows not only to significantly reduce the γ background by requiring coincidences with the transfer products but also to control the beam and its intensity by single particle counting. The predicted large neutron pickup cross-sections of neutron-rich light nuclei on 2H and 9Be targets at REX-ISOLDE energies of 2.2 MeV . A are confirmed.

A 4π silicon ball for detection and identification of light charged particles in large multidetector γ-arrays as EUROBALL is presented. The design is based on a N=42 ball with 12 pentagons and 30 hexagons as used in the GASP array. The absorptive material for γ-rays is minimized to the detector thickness of 300 or 500μm and a 0.63 mm ceramic backing. The geometrical coverage is designed for about 90% of 4π. A pulse shape discrimination method with totally depleted detectors working in the reverse mount allows identifying protons and α-particles above an energy threshold of about 2MeV. The performances of the ball were tested at the tandem – booster accelerator combination of the MPI Heidelberg in two experiments using the high-recoil reaction of 228MeV 58Ni+46Ti and the low-recoil reaction of 95MeV 16O+58Ni. The two-dimensional spectra of zero-crossing (ZC) versus energy confirmed an excellent discrimination of protons and α-particles in all the detectors at different angles. The energy spectra of protons and α-particles measured in the experiments are presented, too. The γ-spectra measured in coincidence with various combinations of emitted particles showed a high selectivity of the ball. The reduced total efficiency for protons of 59% and 55% and α-particles of 44% and 32% measured in a nuclear spectroscopy application is analyzed in a Monte-Carlo simulation (GEANT). It is due to a combined influence of a thick target needed to stop the recoiling residual nuclei and thick absorbers needed to protect the Si-detectors from scattered beam. The results along with the GEANT extrapolation to optimum experimental conditions confirm that RoSiB is a highly efficient and selective device for identification of rare reaction channels with heavy ions.

Picosecond lifetimes in Ba-129.130 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 Ba-129 and twelve states in Ba-130. The resulting B(E2) Values are compared with triaxial rotor plus particle calculations for Ba-129 and, in Ba-130, to the predictions of the general collective model, the interacting boson model, as well as to the symmetric and asymmetric rotor models. In Ba-130, the transitional quadrupole moment in the ground state hand is remarkably constant before and after the backbend. With this data the two-quasiparticle negative parity band in Ba-130 was confirmed to be based on a pi(h(11/2)xd(5/2)/g(7/2)) configuration.

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.

Subpicosecond lifetimes of high spin states in the rotational nuclei 73Se, 74Se and 74Br have been measured using the 58Ni +19F compound reaction and the Doppler Shift Attenuation method. Six EUROBALL Cluster detectors arranged in cube geometry allowed us to select the relevant transitions in γγ coincidence mode. The high counting statistics achieved in this setup also facilitated the determination of average sidefeeding times, which were found to agree rather well with the results of Monte-Carlo calculations of the particle and γ-ray evaporation process. The deduced quadrupole strengths and deformations are compared with the results of previous measurements and the predictions of Cranked Shell Model calculations. In 74Br, a large and constant prolate deformation of β2= 0.37(1) was found for the presumed 4+ and 3− two-quasiparticle bands.

Magnetic dipole moments of excited states in Zr-84 and the N=46 isotones Zr-86 and Nb-87 were measured. The recoil distance transient field method, which is a coincidence technique combining the recoil distance and the transient field methods, was applied. The measurement was performed such that it was sensitive only to those excited states which were populated a few picoseconds after the nuclear reaction. The influence of unobserved continuum feeding on the measured precession angles can thus be neglected. The results are compared with the values obtained using other experimental techniques and with shell model calculations. [S0556-2813(99)01704-5].

The magnetic moments of the 12+ and 11− yrast states in 94Ru and of the 25/2−, 29/2+, and 35/2+ levels in 95Rh have been measured via the IMPAD technique. The nuclei were produced in the reaction 58Ni +40Ca and recoil-implanted into polarized Ni and Fe hosts. The g-factors were deduced from the measured time-integral Larmor precessions. The comparison between the experimental results and large-scale shell model calculations suggests that the 12+ and 11− states in 94Ru and the 25/2− level in 95Rh are pure proton states whereas the 29/2+ and 35/2+ states in 95Rh contain a neutron excitation across the N=50 shell gap. This interpretation supports the conclusion drawn from recent lifetime measurements.