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Bernard Haas 《Acta Physica Hungarica A》1997,6(1-4):205-218
The phenomenon of identical bands is studied by analyzing the distributions of fractional changes in the dynamical moments of inertia of pairs of bands in superdeformed (SD) nuclei. These distributions are found to exhibit a peak with a centroid at nearly zero. Their widths increase in going from the SD bands in the massA~150, to the SD bands in the mass ~190 and to the normally-deformed bands in the rare-earth region. These differences may be attributed to the weaker pairing correlations and the stabilizing role of intruder orbitals on the structures of SD bands. Precise level lifetimes have been measured for various pairs of identical SD bands in Gd and Dy isotopes. By comparing the derived quadrupole moments with calculations performed in the framework of the cranking Skyrme-Hartree-Fock model, it is shown that, independently of the intrinsic configuration and of the proton and neutron numbers, the charge moments calculated with respect to the doubly-magic SD core of152Dy can be expressed in terms of independent contributions from the individual hole and particle orbitals. 相似文献
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I. M. Pavlichenkov 《Physics of Atomic Nuclei》2001,64(6):1093-1097
A semiclassically exact solution for the second inertial parameter B is found for the superfluid and normal phases. An interpolation between these limiting values shows that B changes sign in the transition region at the spin I c that is critical for the rotational spectrum. A superfluid-to-normal transition reveals itself in a specific variation of B versus the spin I. Experimental data show the existence of a transition for superdeformed bands in the A~80, 130, and 150 mass regions and for some bands characterized by a normal deformation. A transition to the normal phase explains the extreme regularity of superdeformed bands. 相似文献
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G. Schönwaßer H. Hübel G.B. Hagemann J. Domscheit A. Görgen B. Herskind G. Sletten J.N. Wilson D.R. Napoli C. Rossi-Alvarez D. Bazzacco R. Bengtsson H. Ryde P.O. Tjøm S.W. Ødegård 《The European Physical Journal A - Hadrons and Nuclei》2002,13(3):291-296
Lifetimes of states in the yrast superdeformed bands of 163Lu and 164Lu were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average
transition quadrupole moments, Q
t = 8.2-0.6
+1.0 b and 7.1-0.6
+0.5 b, were deduced for one of the bands in 163Lu and 164Lu, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in 163Yb, Q
t = 4.9-0.4
+1.3 b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands
correspond to a local potential energy minimum with a pronounced triaxiality, γ∼ 20°.
Received: 8 November 2001 / Accepted: 9 January 2002 相似文献
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C. W. Beausang E. A. Henry J. A. Becker N. Roy S. W. Yates M. A. Deleplanque R. M. Diamond F. S. Stephens J. E. Draper W. H. Kelly J. Burde R. J. McDonald E. Rubel M. J. Brinkman J. A. Cizewski Y. A. Akovali 《Zeitschrift für Physik A Hadrons and Nuclei》1990,335(3):325-330
Two rotational bands, with energy spacings characteristic of superdeformed shapes, have been observed following bombardment of150Nd with48Ca. The more intensively populated band consists of 18 transitions and is assigned to194Hg. The depopulation of this band occurs around spin 10. The second band, consisting of at least 16 transitions, was populated less strongly and is tentatively assigned to194Hg also. The lowest level in this band is assigned spin 8. The energy differences between transitions for both bands decrease from ~40 keV at low rotational frequencies to ~30 keV at the highest observed frequencies. The moments of inertia of the bands are similar to those of the two previously observed superdeformed bands in191,192Hg. The similarities and differences of the four known bands in the mercury region are discussed. 相似文献
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I. M. Pavlichenkov 《JETP Letters》2000,71(1):4-7
The quasiclassically exact solution for the second inertial parameter ? is found in a self-consistent way. It is shown that superdeformation and nonuniform pairing arising from the rotation-induced pair density significantly reduce this parameter. The new signature for the transition from pairing to normal phase is suggested in terms of the variation ?/A versus spin. Experimental data indicate the existence of such a transition in the three SD mass regions. 相似文献
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R. Krücken Z. Wang S.J. Asztalos J.A. Becker L.A. Bernstein R.M. Clark M.A. Deleplanque R.M. Diamond P. Fallon N. Fotiades K. Hauschild I.Y. Lee A.O. Macchiavelli G.J. Schmid F.S. Stephens K. Vetter 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):367-370
Lifetimes of states in the two strongest superdeformed (SD) bands in 193Tl were measured using the Doppler-shift attenuation method. The reaction 176Yb(23Na,6n)193Tl at a beam energy of 129 MeV was used and γ-rays were detected by the Gammasphere array. Quadrupole moments of 18.3(10)
eb and 17.4(10) eb were extracted for SD bands 1 and 2, respectively, using the fractional Doppler-shifts of the SD transitions.
The previously reported linking transitions of these SD bands to normal deformed near yrast levels could not be confirmed.
No other candidates for linking transitions could be established.
Received: 27 April 1999 相似文献
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C. Finck O. Stézowski F.A. Beck D.E. Appelbe T. Byrski S. Courtin D.M. Cullen D. Curien G. de France G. Duchêne S. Ertürk B.J.P. Gall U. Garg B. Haas N. Khadiri B. Kharraja N. Kintz A. Nourreddine D. Prévost C. Rigollet H. Savajols P.J. Twin J.P. Vivien K. Zuber 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):123-127
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Cederwall B Janssens RV Brinkman MJ Lee IY Ahmad I Becker JA Carpenter MP Crowell B Deleplanque MA Diamond RM Draper JE Duyar C Fallon P Farris LP Henry EA Henry RG Hughes JR Khoo TL Lauritsen T Macchiavelli AO Rubel E Stephens FS Stoyer MA Satula W Wiedenhoever I Wyss R 《Physical review letters》1994,72(20):3150-3153
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The current status of the ΔI=4 bifurcation in superdeformed bands is reviewed by making use of a theoretical model based on the interaction of rotation and single-particle nucleon motion in nuclei with an axial deformation. It is shown that the hexadecapole-type distortion of a nuclear shape by rotation is especially important for explaining the phenomenon. The necessary condition for staggering is obtained from an analysis of the nonadiabatic effect of rotation. This criterion is applied to 30 superdeformed bands in the mass region around A ~ 150. An analysis confirms the configuration-dependence effect and allows us to discriminate between single-particle states active and inactive for staggering. The consideration is based on the additivity of the nonaxial hexadecapole moment, which plays a key role in the staggering phenomenon. 相似文献
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E.F. Moore M.P. Carpenter R.V.F. Janssens T.L. Khoo T. Lauritsen D. Ackermann I. Ahmad H. Amro D. Blumenthal S. Fischer G. Hackman D. Nisius F. Hannachi A. Lopez-Martens S. J. Asztalos R.M. Clark M.A. Deleplanque R.M. Diamond P. Fallon R. Krueken I-Y. Lee A.O. Macchiavelli F.S. Stephens J.A. Becker L. Bernstein L.P. Farris E.A. Henry A. Korichi 《Zeitschrift für Physik A Hadrons and Nuclei》1997,358(2):219-223
The lifetimes of states in Superdeformed (SD) bands in 192,194Hg have been measured using the Doppler shift attenuation method. Intrinsic quadrupole moments have been extracted for band 1 of 192Hg and for bands 1, 2, and 3 of 194Hg. It was found that the quadrupole moments for the “identical” SD bands in these nuclei are the same. In the same experiment, one-step transitions linking SD states to yrast and near yrast states for bands 1 and 3 of 194Hg have been identified. From this observation, excitation energies, spins and probable parities have been assigned to SD states in these bands. 相似文献
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I. M. Pavlichenkov 《Physics of Atomic Nuclei》2002,65(7):1198-1218
We derive an exact semiclassical expression for the second inertial parameter B for superfluid and normal phases. Interpolation between these limiting values shows that the function B(I) changes sign at the spin I c that is critical for the rotational spectrum. The quantity B proves to be a sensitive measure of the change in static pairing correlations. The superfluid-to-normal transition reveals itself in a specific variation of the ratio B/A versus the spin I with a plateau characteristic of the normal phase. We find this dependence to be universal for normal deformed and superdeformed bands. A long plateau with a small value of B/A ~ A ?8/3 explains the extreme regularity of superdeformed bands. 相似文献
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U. J. van Severen W. Korten H. Hübel D. Bazzacco G. LoBianco N. H. Medina C. Rossi Alvarez S. Signorelli K. Strähle P. Willsau 《Zeitschrift für Physik A Hadrons and Nuclei》1995,353(1):15-16
Two excited superdeformed bands have been found in196Pb using the GASP-ray spectrometer array. They are signature-partner bands with a small signature splitting developing at higher frequencies, similar to bands 2 and 3 in the isotone194Hg. The bands are probably built on an excited neutron configuration. They show an unusual incremental alignment of 1/2 with respect to the194Pb core.Communicated by: B. Herskind 相似文献