E.H. Spejewski

The structure of high spin states in 184Hg and 186Hg

Abstract The structure of 184 Hg has been studied through the 156 Gd( 32 S, 4n) reaction. The spins of the levels up to 18 + were established by measuring directional correlation ratios from oriented nuclei. Mean lifetimes of the levels from 8 + to 18 + were measured by the Doppler shift attenuation method. The deduced |β 2 | values are nearly constant to indicate a stable nuclear shape. The deformed band (up to tentative spin 24 + ) shows two upbendings at h ω ∼ 0.26 MeV and h ω ∼ 0.33 MeV . Cranked shell-model calculations suggest that these band-crossings can be associated with v i 13 2 and π h 9 2 pairs at prolate shape. A new interpretation of previously reported band structures in 186 Hg is given.

Present status of the unisor facility

Abstract The UNISOR facility is an ISOL system at the Oak Ridge National Laboratory,primarily intended for radioactive-decay measurements. The current status of the facility is described including available accelerator beams, targets and ion sources, separator beam-lines and source handling equipment, and data acquisition systems.

Ground state shaoe and crossing of near spherical and deformed bands in 182Hg

Abstract The energy levels of 182 Hg have been identified for the first time through comparison of in-beam studies of the reactions 156,154 Gd( 32 S, 4n) 184,182 Hg and γ-X-ray coincidences. Levels up to 12 + in 182 Hg were established from γ-γ coincidences and singles measurements. The data establish that the ground state shape is near spherical, and that the ground band is crossed by a well-deformed band at 4 + . In contrast to IBA model predictions that the deformed band will rise in energy in 182 Hg compared to 184 Hg, the energies of the deformed levels in 182 Hg continue to drop.

The CARDS array for neutron-rich decay spectroscopy at HRIBF

An array for decay studies of neutron-rich nuclei has been commissioned for use at the UNISOR separator at Holifield Radioactive Ion Beam Facility. This array consists of three segmented clover Ge detectors, plastic scintillators, and a high-resolution (∼1 keV) Si conversion electron spectrometer. These detectors are mounted on a support that surrounds a moving tape collector. This system has been named clover array for radioactive decay studies. The detectors have been outfitted with digital flash ADCs (XIA DGFs) that fit the preamp signals, with built-in pileup rejection.

An ohmic-heated thermal-ionization source

Abstract A thermal-ionization ion-source intended for on-line use at the UNISOR facility is described. This source is a compact design, well heat-shielded, and is directly heated by a helical filament. It has been operated at temperatures in excess of 2300 K at an input power of 800 W.

Collective and noncollective states in Cd-116 studied via the beta decays of Ag-116m1, m2, gs

We have re-investigated the beta decay of the three isomers of

Collective and Non-Collective States in 116Cd Studied via the Beta-Decays of 116Agm1,m2,gs

^{116}

Yields of fission products from various uranium and thorium targets.

Ag at the Holifield Radioactive Ion Beam Facility (HRIBF). Through the use of half-life information, we have been able to construct individual decay schemes for each isomer, and correct what was a puzzling inconsistency with the published data, namely the beta feeding of 2