High-spin states in 222Th |
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Authors: | D Ward GD Dracoulis JR Leigh RJ Charity DJ Hinde JO Newton |
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Institution: | Department of Nuclear Physics, Research School of Physical Sciences, Australian National University, PO Box 4, ACT 2600, Australia |
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Abstract: | Levels to spin 16+ in the ground band and 17? in the octupole band in 222Th have been identified using the reaction 208Pb(18O, 4n)222Th at 93 MeV. To suppress intense γ-ray background from fission a residue detector was built and operated in coincidence with the Ge(Li) and NaI(Tl) detectors. The apparent moment of inertia in the ground-state rotational band rises very rapidly with increasing spin, however, no indications of backbending were observed. The octupole band at low spin has an aligned angular momentum relative to the ground-state band. Strong cross-band E1 transitions competed with collective E2 transitions within each band. Analysis showed that the ratios were within experimental uncertainty independent of both the spin and parity of the parent state.The average γ-ray multiplicity per cascade was measured for 222Th. The results were in reasonable agreement with the computer code ORNL-ALICE. |
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Keywords: | Nuclear reactions |
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