145 research outputs found
Excitation energy and deformation of the 1/2+[431] intruder band in
The already detailed study of nucleus was complemented by a search for microsecond isomers at very low energy. For this purpose, this neutron-rich nucleus was produced by thermal-neutron-induced fission of . We have found a new 30.1 keV microsecond isomeric state which deexcites to the ground state by a strongly-hindered E1 transition. This isomer was identified as the 3/2+ level of the 1/2+[431] intruder band in and is also the lowest-lying member of the band. The very low energy of the band head suggests a large quadrupole deformation. From a comparison with ,where more information is known about the intruder band, it is deduced that the 1/2+[431] band has a quadrupole deformation, 0.35 and a possible triaxial shape, 20°
First observation of low-lying excited states in the very neutron-rich
Microsecond isomers of neutron-rich nuclei in the mass A=95 chain were investigated at the ILL reactor, Grenoble. These nuclei were produced by thermal-neutron induced fission of . The detection is based on time correlation between fission fragments selected by the Lohengrin mass spectrometer and the -rays from the isomers. In this paper the decay scheme of an isomer of half life 1.4(2) micro second in is reported. It is the first time that excited states of this nucleus have been measured. These data show that this neutron rich N = 59 isotone is spherical at low excitation energy
Shape coexistence in the very neutron-rich odd-odd
Microsecond isomers of neutron-rich nuclei in the masses A=96 and 98 were reinvestigated at the ILL reactor (Grenoble). These nuclei were produced by thermal-neutron induced fission of Pu. The detection is based on time correlation between fission fragments selected by the Lohengrin mass spectrometer, and the rays and conversion electrons from the isomers. A new level scheme of Rb is proposed. We have found that the ground state and low-lying levels of this nucleus are rather spherical, while a rotational band develops at 461 keV energy. This bans has properties consistent with a Nilsson assignment and a deformation . It is fed by a microsecond isomer consistent with a sperical configuration. It is interesting to note that the same unique-parity states and are present in the same nucleus in a deformed and in a spherical configuration. The neighbouring odd-odd nucleus Y presents a strong analogy with Rb and is also discussed
High spin microsecond isomers in In and Sb
In this work the microsecond isomers in 129In and 129Sb were investigated. These nuclei were produced by the thermal-neutron-induced fission of 241Pu. The detection is based on a time correlation between the fission fragments selected by the LOHENGRIN spectrometer at the ILL (Grenoble) and the Îł rays or conversion electrons from the isomers. The decay schemes of the new 17/2â isomer in 129In and 23/2+ isomer in 129Sb are reported. A shell-model study of these two nuclei was performed using a realistic effective interaction derived from the CDâBonn nucleon-nucleon potential. Comparison shows that the calculated energy levels and electromagnetic transition rates are in very good agreement with the experimental data. (APS
Recent measurements of the spherical and deformed isomers using the Lohengrin fission-fragment spectrometer
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New Spins for ground states and isomers in Pd and Pd
Levels in 115Pd and 117Pd nuclei, populated in the spontaneous fission of 248Cm were studied by means of prompt gamma spectroscopy using the EUROGAM2 array of Anti-Compton spectrometers. Negative-parity, I = 9/2 excitations were identified, which are associated with the long-lived isomers in these nuclei, reported previously as 11/2- excitations. The new data indicate spin and parity 3/2 + for ground states in 115Pd and 117Pd instead of 5/2 + proposed in previous works. This result implicates changes of spin assignments to other levels in both nuclei
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