183 research outputs found
Wobbling excitations at high spins in A~160
We found that in 156Dy and 162Yb the lowest odd spin gamma-vibrational states
transform to the wobbling excitations after the backbending, associated with
the transition from axially-symmetric to nonaxial shapes. The analysis of
quadrupole electric transitions determines uniquely the sign of the
gamma-deformation in both nuclei after the transition point.Comment: 6 pages, 4 figure
COEXISTENCE DES FORMES ALLONGÉE ET APLATIE DANS 187Au
187Au a été étudié simultanément par réaction 175Lu(16O, 4n)l87Au au cyclotron à énergie variable d'Orsay, et par étude de la désintégration radioactive de 187Hg (T½ = 133 ± 13 ns) à l'aide du séparateur Isocèle en ligne sur le synchrocyclotron de l'IPN d'Orsay. Les résultats obtenus ont été comparés à ceux du coeur pair-pair 186Pt formé par réaction 174Yb(16O, 4n)186Pt. On a ainsi mis en évidence deux bandes découplées construites dans les couches h 11/2 et h 9/2 indiquant des déformations respectivement oblate et prolate comme dans 189Au [1]. Dans la bande h 9/2, bien développée, de même que dans le coeur 186Pt, on a pu mettre en évidence un effet de backbending : ceci permet de penser qu'il est essentiellement dû à une paire de protons h 11/2 (blocking du proton h 9/2 aligné sur le cœur)
Superdeformation in Po
The Yb(Si,5n) reaction at 148 MeV with thin targets was used
to populate high-angular momentum states in Po. Resulting rays
were observed with Gammasphere. A weakly-populated superdeformed band of 10
-ray transitions was found and has been assigned to Po. This is
the first observation of a SD band in the region in a nucleus
with . The of the new band is very similar to those of
the yrast SD bands in Hg and Pb. The intensity profile suggests
that this band is populated through states close to where the SD band crosses
the yrast line and the angular momentum at which the fission process dominates.Comment: 10 pages, revtex, 2 figs. available on request, submitted to Phys.
Rev. C. (Rapid Communications
Chaos in Axially Symmetric Potentials with Octupole Deformation
Classical and quantum mechanical results are reported for the single particle
motion in a harmonic oscillator potential which is characterized by a
quadrupole deformation and an additional octupole deformation. The chaotic
character of the motion is srongly dependent on the quadrupole deformation in
that for a prolate deformation virtually no chaos is discernible while for the
oblate case the motion shows strong chaos when the octupole term is turned on.Comment: 6 pages LaTex plus 4 figures available by contacting the authors
directly, published in PHYS.REV.LETT. 72(1994) 235
Spin-rotor Interpretation of Identical Bands and Quantized Alignment in Superdeformed A 190 Nuclei
The ``identical'' bands in superdeformed mercury, thallium, and lead nuclei
are interpreted as examples of orbital angular momentum rotors with the weak
spin-orbit coupling of pseudo- symmetries and supersymmetries.Comment: 15 pages, revtex 3.0, 7 figures available upon request from
[email protected]
Deducing the \u3csup\u3e237\u3c/sup\u3eU(\u3cem\u3en,f\u3c/em\u3e) Cross Section Using the Surrogate Ratio Method
We have deduced the cross section for 237U(n, f) over an equivalent neutron energy range from 0 to 20 MeV using the surrogate ratio method. A 55 MeV4He beam from the 88 inch cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions: 238U(α, αf) and 236U(α, αf). The 238U reaction was a surrogate for 237U(n, f), and the 236U reaction was used as a surrogate for 235U(n, f). Scattered α particles were detected in a fully depleted segmented silicon telescope array over an angle range of 35° to 60° with respect to the beam axis. The fission fragments were detected in a third independent silicon detector located at backward angles between 106° and 131°
High-\u3cem\u3eK\u3c/em\u3e Multi-quasiparticle States and Rotational Bands in \u3csup\u3e255\u3c/sup\u3e\u3csub\u3e103\u3c/sub\u3eLr.
Two isomeric states have been identified in 255Lr. The decay of the isomers populates rotational structures. Comparison with macroscopic-microscopic calculations suggests that the lowest observed sequence is built upon the [624]9/2+ Nilsson state. However, microscopic cranked relativistic Hartree-Bogoliubov (CRHB) calculations do not reproduce the moment of inertia within typical accuracy. This is a clear challenge to theories describing the heaviest elements
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