279 research outputs found
Sequential ejectile decays and uncorrelated breakup processes in the 14N + 159Tb reaction
From a study of particle-particle correlations, involving position-sensitive detector telescopes, conclusive evidence for sequential ejectile decay was found, and the relative importance of sequential decay and of breakup processes, which were observed to be uncorrelated in angle, could be determined
High-spin states in 232U investigated with the 232Th(α, 4nγ) reaction
The ground-state rotational band of 232U is established up to Iπ = 16+ (tentatively 18+) through a study of the 232Th(α, 4nγ) reaction. Conversion electron spectroscopy is found to be especially useful in circumventing the difficulties caused by strong fission competition
Evolution of the one-phonon 2(1,ms)(+) mixed-symmetry state in N=80 isotones as a local measure for the proton-neutron quadrupole interaction
An inverse kinematics Coulomb excitation experiment was performed to obtain absolute E2 and M1 transition strengths in 134Xe. The measured transition strengths indicate that the 23+ state of 134Xe is the dominant fragment of the one-phonon 21, ms+ mixed-symmetry state. Comparing the energy of the 21, ms+ mixed-symmetry state in 134Xe to that of the 21, ms+ levels in the N = 80 isotonic chain indicates that the separation in energy between the fully-symmetric 21+ state and the 21, ms+ level increases as a function of the number of proton pairs outside the Z = 50 shell closure. This behavior can be understood as resulting from the mixing of the basic components of a two-fluid quantum system. A phenomenological fit based on this concept was performed. It provides the first experimental estimate of the strength of the proton-neutron quadrupole interaction derived from nuclear collective states with symmetric and antisymmetric nature
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Core of F 25 studied by the F 25 (-p) proton-removal reaction
The Be9(BeF25(5/2+),BeO24)X proton-removal reaction was studied at the NSCL using the S800 spectrometer. The experimental spectroscopic factor for the ground-state to ground-state transition indicates a substantial depletion of the proton d5/2 strength compared to shell-model expectations, similar to the findings of an inverse-kinematics (p,2p) measurement performed at RIBF. The BeF25 to BeO24 ground-states overlap is considerably less than anticipated if the core nucleons behaved as rigid, doubly-magic BeO24 within BeF25. We interpret the new results within the framework of the Particle-Vibration Coupling (PVC) model, of a d5/2 proton coupled to a quadrupole phonon of an effective core. This approach provides a good description of the experimental data, requiring an effective BeO∗24 core with a phonon energy of ħω2= 3.2 MeV and a B(E2)≈2.7 W.u. - softer and more collective than a bare BeO24. Both the Nilsson deformed mean field and the PVC models appear to capture the properties of the effective core of BeF25, suggesting that the additional proton polarizes BeO24 in such a way that it becomes either slightly deformed or a quadrupole vibrator
Possible quenching of static neutron pairing near the N=98 deformed shell gap: Rotational structures in Gd-160,Gd-161
A Gd160 beam was accelerated to an energy of 1000 MeV and, separately, bombarded thick targets of Sm154 and Dy164 in order to observe neutron-rich, rare-earth nuclei via deep-inelastic collision processes. Gammasphere was utilized to observe ?-ray emissions. Many new states and transitions were observed in Gd160 as a result of so-called unsafe Coulomb excitation. The ground-state band in Gd160 has been extended to Ip=20+ and a rotational band based on the Kp=4+ state, previously associated with a hexadecapole vibration, was observed up to 18+. The quasiparticle configuration of the Kp=4+ band has been determined, and its unusual alignment behavior may result from a possible quenching of static neutron pairing. In addition, the band based on the [523]5/2 quasineutron orbital in Gd161 was extended from 11/2- to 33/2- and also displays the same unusual alignment behavior
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