Excited states in Y-98, populated in neutron-induced fission of U-235 and in spontaneous fission of Cm-248 and Cf-252, have been studied by means of gamma spectroscopy using the Lohengrin ...fission-fragment separator at ILL Grenoble and the EXILL, Eurogam2, and Gammasphere Ge arrays. Two new isomers have been found in Y-98: a deformed one with T-1/2 = 180(7) ns and a rotational band on top of it, and a spherical one with T-1/2 = 0.45(15) mu s, analogous to the 8(+) isomer in Y-96, corresponding to the (nu g(7/2), pi g(9/2))(8+) spherical configuration. Using the JYFLTRAP Penning trap, an accurate excitation energy of 465.7(7) keV has been determined for the 2.36-s isomer in Y-98. This result and the studies of excited levels in Zr-98, populated in beta-decay of the isomer, indicate a new spin-parity, I-pi = (7)(+) for the isomer. The high spin and the decay properties of this isomer suggest the presence of the 9/2(+) 404 neutron extruder orbital in its structure. This is consistent with the large deformation of the isomer, reported recently. The present work does not provide arguments to support the special role of the nu g(7/2)-pi g(9/2) interaction (the spin-orbit-partner, or SOP, mechanism).
Two neutron-rich N=93 isotones, {sup 155}Sm and {sup 153}Nd, have been studied by delayed gamma-ray and conversion-electron spectroscopy at the Lohengrin mass spectrometer. A half-life of 2.9(5) mus ...has been measured for the nu5/2{sup +}642 state at 16.5 keV in {sup 155}Sm. The decay of a 1.17(7)-mus isomer in {sup 153}Nd, at 191.7 keV, has been remeasured and its spin has been reassigned as (5/2){sup +}. This state contains a strong component of the nu5/2{sup +}642 Nilsson orbital. In addition, a new 1.00(8)-mus isomeric state at 538.6 keV, with a probable nu11/2{sup -}505 Nilsson configuration, has been observed in {sup 155}Sm. Triple gamma-ray coincidence data from the spontaneous fission of a {sup 252}Cf source placed inside the Gammasphere array were used to extend the collective band on top of the (5/2{sup +}) isomeric state of {sup 153}Nd, and a new band with the same bandhead spin has been observed in {sup 151}Ce. The observation of this new band and an additional new transition in the ground-state band has led us to change the ground-state spin of {sup 151}Ce to (3/2{sup -}). Calculations using the quasiparticle-rotor model successfully reproduce the majority of the features of the gamma decays of these nuclei, including branching ratios and isomeric half-lives. Because this model uses a reflection-symmetric core, we conclude that the polarizing effect of the odd particle is responsible for the dipole moment present in the nu5/2{sup +}642 states of the three nuclei studied and the nu11/2{sup -}505 level of {sup 155}Sm.
An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 10
9 ppp) proton beam from CERN-PS at several kinetic energies from ...600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically
G ≈ 30 in reasonable agreement with calculations, where
G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which
G decreases but is still acceptable in the energy range explored
The decay of a T1/2 19(3) μs isomeric state from 125Cd has been observed using γ-ray spectroscopy at the Lohengrin mass spectrometer of the Institut Laue-Langevin, Grenoble. Two coincident γ rays ...were observed to be emitted from the decay of this isomeric state, contradicting recently published data on this nucleus. Realistic shell-model calculations have been performed to interpret the decay scheme, allowing a spin and parity of 19/2+ to be assigned to the isomeric state. All configurations contributing to this isomeric state have amplitudes less than 7 %. Experimental data have recently been published on the decays of μs isomeric states in 127,128,130Cd. Realistic shell-model calculations for these nuclei are presented which reproduce the known experimental decay schemes reasonably well.
The already detailed study of {sup 107}Tc 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 {sup 241}Pu. 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{sup +} level of the 1/2{sup +}431 intruder band in {sup 107}Tc 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 {sup 105}Tc, where more information is known about the intruder band, it is deduced that the 1/2{sup +}431 band has a quadrupole deformation, {epsilon}{sub 2}{>=}0.35 and a possible triaxial shape, {gamma}{approx_equal}20 degrees.
In this work microsecond isomers in {sup 130,132}Te and {sup 134}Xe are investigated. These nuclei are produced by thermal neutron induced fission of {sup 239}Pu and {sup 241}Pu. The detection is ...based on time correlation between fission fragments selected by the LOHENGRIN spectrometer at ILL (Grenoble) and the {gamma} rays or conversion electrons from isomers. The 10{sup +}{yields}8{sup +} isomeric transition of {sup 132}Te and {sup 134}Xe was measured for the first time and the half-life of the analogous transition in {sup 130}Te was remeasured. The systematic behavior of the B(E2) values of this isomeric transition is studied in Sn, Te, Xe, and Ba isotopes close to {sup 132}Sn. A simple mechanism is proposed to explain the strong increase in the B(E2) strengths from the Sn to the Te isotones.
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![The ν9/2[404] orbital and t...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1434-6001/small "The ν9/2[404] orbital and the deformation in the A ∼ 100 region")
