J.A. Winger

The wobbling mode in 167Lu

Abstract High spin states in 167 Lu were populated through the 123 Sb( 48 Ca, xn ) reaction at 203xa0MeV. Four, presumably triaxial, strongly deformed (TSD) bands have been found in this nucleus. Several transitions linking an excited TSD band (TSD2) to the lowest (yrast) TSD band (TSD1) were observed. The electromagnetic properties of the connecting transitions have been investigated. Evidence for the assignment of TSD2 as a wobbling mode built on TSD1 is presented. This assignment is based on comparisons of the experimental data to theoretical calculations. The wobbling mode of excitation is an unambiguous signal of a stable triaxial deformation associated with these bands.

Identification of 181Hg and shape coexistence in odd-A Hg isotopes

Abstract In-beam γ-ray transitions in 181 Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed 1 2 − [521] ground state was observed up to 29 2 − . A 5 2 − [512] configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron i 13 2 orbitals and are proposed to decay to an i 13 2 isomeric state associated with an oblate state.

decay of 72Co and microsecond isomers in even-mass neutron-rich nickel isotopes

A new excited state at 2164 keV has been identified in 72Ni with tentative spin and parity of 4+ based on comparison to shell model calculations. This level is suggested to be populated via the ?-decay of an isomeric state in 72Co, and is postulated to be one of the key states that play a role in the disappearance of isomers in Ni. The known low-energy levels in 72Ni are compared with results of shell model calculations using the NR78 interaction to follow the seniority of the observed states. In addition, the half-life of the 8+ isomer in 76Ni has been measured as 630(90) ns and the full cascade of transitions from this isomer has been verified experimentally in this work.

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.

Towards new proton radioactivities with radioactive beams and digital signal processing

Abstract Particle radioactivity studies using the XIA DGF-4C digital signal processing units at the Recoil Mass Separator of Oak Ridge National Laboratory are presented. Proton emission signals were observed starting from 500 ns after recoil implantation. An energy threshold below 100 keV for particle detection was achieved. For the 145 Tm and 146 Tm decay, evidence for the fine structure in proton emission was obtained. An experiment to search for a new proton emitter 149 Lu is described as an example where the combination of a 56 Ni radioactive beam and digital signal processing is a major advantage.

Studies of light nuclei beyond the particle driplines: the two-proton emitter 12O

Abstract The decay dynamics of the ground state two proton emitter 12O, which lies beyond the proton dripline, were investigated following the population of 12O via single-neutron stripping of an 13O projectile. The decay products, two protons and 10C, were detected in coincidence and correlations among these particles were studied. No evidence was seen for 2He emission in the decay. This appears consistent with direct breakup or possibly sequential decay through 11N.

First observation of excited states in 140Dy

The mass A = 140 products of the 54Fe (315 MeV) + 92Mo reaction were selected by a recoil mass spectrometer and studied in a recoil ‐ delayed γ‐γ coincidence experiment. A new 7 μs isomer was identified in the drip line nucleus 140Dy. Five cascading γ transitions were assigned to the decay of the Iπ = 8− {v9/2−[514] ⊗ v7/2+[404]} K isomer via the ground state band transitions. The established structure of 140Dy is discussed with reference to the fine structure in proton decay of 141Ho.

Triaxiality and The Wobbling Mode In 167Lu

High spin states in 167Lu nucleus were populated through the 123Sb(48Ca,xn) reaction at 203 MeV. Five presumably triaxial superdeformed (TSD) bands have been found. The electromagnetic properties of several connecting transitions between the yrast (TSD1) and the excited (TSD2) bands have been established. Evidence for the assignment of TSD2 band as a wobbling mode built on the yrast TSD band is presented. These bands coexist with bands built on quasiparticle excitations in normal deformed (ND) minimum for which new data are also presented.