0000000000482663
AUTHOR
S. Vinals
Decay studies of the long-lived states in Tl-186
9 pags., 12 figs., 3 tabs.
New β-decaying state in 214Bi
A new β-decaying state in 214Bi has been identified at the ISOLDE Decay Station at the CERN-ISOLDE facility. A preferred Iπ = (8−) assignment was suggested for this state based on the β-decay feeding pattern to levels in 214Po and shell-model calculations. The half-life of the Iπ = (8−) state was deduced to be T1/2 = 9.39(10) min. The deexcitation of the levels populated in 214Po by the β decay of this state was investigated via γ -γ coincidences and a number of new levels and transitions was identified. Shell-model calculations for excited states in 214Bi and 214Po were performed using two different effective interactions: the H208 and the modified Kuo-Herling particle interaction. Both ca…
Competition between allowed and first-forbidden β decays of At208 and expansion of the Po208 level scheme
The structure of 208Po populated through the EC/β+ decay of 208At is investigated using γ-ray spectroscopy at the ISOLDE Decay Station. The presented level scheme contains 27 new excited states and 43 new transitions, as well as a further 50 previously observed γ rays which have been (re)assigned a position. The level scheme is compared to shell model calculations. Through this analysis approximately half of the β-decay strength of 208At is found to proceed via allowed decay and half via first-forbidden decay. The first-forbidden transitions predominantly populate core excited states at high excitation energies, which is qualitatively understood using shell model considerations. This mass r…
Evolution of Octupole Deformation in Radium Nuclei from Coulomb Excitation of Radioactive Ra222 and Ra228 Beams
There is sparse direct experimental evidence that atomic nuclei can exhibit stable "pear" shapes arising from strong octupole correlations. In order to investigate the nature of octupole collectivity in radium isotopes, electric octupole (E3) matrix elements have been determined for transitions in ^{222,228}Ra nuclei using the method of sub-barrier, multistep Coulomb excitation. Beams of the radioactive radium isotopes were provided by the HIE-ISOLDE facility at CERN. The observed pattern of E3 matrix elements for different nuclear transitions is explained by describing ^{222}Ra as pear shaped with stable octupole deformation, while ^{228}Ra behaves like an octupole vibrator.
Measurement of the 2+→0+ ground-state transition in the β decay of F20
We report the first detection of the second-forbidden, nonunique, 2+→0+, ground-state transition in the β decay of F20. A low-energy, mass-separated F+20 beam produced at the IGISOL facility in Jyvaskyla, Finland, was implanted in a thin carbon foil and the β spectrum measured using a magnetic transporter and a plastic-scintillator detector. The β-decay branching ratio inferred from the measurement is bβ=[0.41±0.08(stat)±0.07(sys)]×10-5 corresponding to logft=10.89(11), making this one of the strongest second-forbidden, nonunique β transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars tha…
The observation of vibrating pear-shapes in radon nuclei
6 pags., 4 fig.s, 1 tab. -- Open Access funded by Creative Commons Atribution Licence 4.0