High-spin states in Kr-77 were identified via analysis of prompt gamma-gamma coincidences in the Ni-58(Si-29,2 alpha 2p) reaction at 128 MeV at the Gammasphere facility. Evaporation channel selection ...was achieved using the 95 element Microball charged-particle detector. 27 new states and 42 new transitions were found, The positive-parity bands were confirmed and the alpha=-1/2 band extended to 39/2(+). The negative-parity signature pair was extended to 31/2(-) and 37/2(-). Two new high-lying negative-parity bands were found extending from a state of spin I = 15/2 and energy 2.6 MeV to 17.4 MeV at I = (55/2). The new bands appear highly deformed and become yrast at high spin. A three-quasiparticle structure based on deformation driving, low-K unique-parity and intruder orbitals is suggested for them.
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Lifetimes of states within a triaxial band belonging to;the gamma-soft nucleus Ce-133 have been determined through a Doppler-broadened line shape analysis. A value, Q(t)approximate to 2.2 eb, has ...been found for the transition quadrupole moment which is considerably smaller than that of superdeformed structures (Q(t)approximate to 7.4 e b) in this mass region. The results are discussed in terms of deformation self-consistent calculations based on the total Routhian surface formalism. S0556-2813(98)01912-8.
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The technique of recoil beta tagging has been developed which allows prompt gamma decays in nuclei from excited states to be correlated with electrons from their subsequent short-lived beta decay. ...This technique is ideal for studying nuclei very far from stability and improves in sensitivity for very short-lived decays and for high decay Q-values. The method has allowed excited states in 78Y to be observed for the first time, as well as an extension in the knowledge of T=1 states in 74Rb. From this new information it has been possible to compare Coulomb energy differences (CED) between T=1 states in 70Br/70Se, 74Rb/74Kr, and 78Y/78Sr. The A=70 CED exhibit an anomalous behavior which is inconsistent with all other known CED. This behavior may be accounted for qualitatively in terms of small variations in the Coulomb energy arising from shape changes.
A new generation of high-resolution hypernuclear gamma$-spectroscopy
experiments with high-purity germanium detectors (HPGe) are presently designed
at the FINUDA spectrometer at DAPhiNE, the Frascati ...phi-factory, and at PANDA,
the antiproton proton hadron spectrometer at the future FAIR facility. Both,
the FINUDA and PANDA spectrometers are built around the target region covering
a large solid angle. To maximise the detection efficiency the HPGe detectors
have to be located near the target, and therefore they have to be operated in
strong magnetic fields B ~ 1 T. The performance of HPGe detectors in such an
environment has not been well investigated so far. In the present work VEGA and
EUROBALL Cluster HPGe detectors were tested in the field provided by the ALADiN
magnet at GSI. No significant degradation of the energy resolution was found,
and a change in the rise time distribution of the pulses from preamplifiers was
observed. A correlation between rise time and pulse height was observed and is
used to correct the measured energy, recovering the energy resolution almost
completely. Moreover, no problems in the electronics due to the magnetic field
were observed.
We discuss the appearance of Deltaital I=2 staggering effects in the gamma-ray energies of some superdeformed bands as due to the mixing of a series of ital K bands. These bands are described by the ...rotational Hamiltonian of a symmetric top having a fourfold symmetry axis. Using the known properties of superdeformed bands we have found limits to the possible values of the model parameters by the analysis of effective moments of inertia, deviations from the ital I(ital I+1) rigid-rotor behavior and ital B(ital E2) values. Our results indicate that the value of Isub 3, the moment of inertia due to the ital Ysub 44 deformation, is close to that expected for a rigid ellipsoid.
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This report presents scintillator devices based on BaF/sub 2/ and YAP:Ce crystals for particle detection and beam monitoring of singly and highly charged ions in the CRYRING storage ring. The ...scintillator materials fulfil the requirement of the Extreme Ultra High Vacuum of the order of 10/sup -12/ mbar. Both crystals are known to be very fast responding scintillators. The BaF/sub 2/ crystal is mounted as a vacuum window with the PM-tube attached outside. This setup has been used for many years without any indication of deterioration, confirming the high radiation hardness of BaF/sub 2/. The device employing a YAP:Ce crystal is placed inside the vacuum tube, close to the circulating heavy ion beam. Methods have been developed for efficient transmission of the scintillation light to the PM-tube placed outside vacuum. The presented detector systems have been employed in measurements of atomic lifetimes, detection of 1 GeV Pb ions and heavy ion beams electron cooled to ordering.
Gamma-ray lines from Sn-103 have been identified for the first time using EUROBALL and ancillary detectors. The level scheme of Sn-103 has been established by means of particle-gated gamma gamma ...coincidences. The energy spacing between the g(7/2) and d(5/2) neutron single-particle orbitals is determined from the excited states in Sn-103.
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