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Zamfir, N.V.; Casten, R.F.
Yale Univ., New Haven, CT (United States); Clark Univ., Worcester, MA (United States)2000
Yale Univ., New Haven, CT (United States); Clark Univ., Worcester, MA (United States)2000
AbstractAbstract
[en] The nature and evolution of collectivity and coherence in nuclei is one of the most fundamental issues in nuclear structure and its evolution with N and Z. Despite many experiments, the nature of nuclear vibrational modes in deformed nuclei and the nature of nuclear phase/shape transitions are not at all understood. The authors discuss new experiments on phonon and multi-phonon states in the rare earth nuclei and on new evidence for phase coexistence in Sm that relates to the possible existence of phase transitional behavior in finite nuclei
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Applications of High-Precision γ-Spectroscopy; Notre Dame, IN (United States); 1-3 Jul 1998; FG02-91ER40609; FG02-88ER40417
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Journal of Research of the National Institute of Standards and Technology; ISSN 1044-677X;
; CODEN JRITEF; v. 105(1); p. 147-152

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[en] The energy ratio of the first excited states of even-even nuclei R4/2 triple-bond E(4+1)/E(2+1), is an excellent signature of structure, varying smoothly from <2 in open-quotes precollectiveclose quotes nuclei to 3.33 for good rotors. We will discuss this phenomenology, in terms of the extremely simple idea that a high R4/2 results when the wave function has large amplitudes for pairs of orbits, differing by Δj=2, each orbit occupied by an odd numbers of nucleons. In such a case, the angular momenta must be co-planar leading to a large attractive interaction energy. This explains why light 2-valence nucleon nuclei such as 18O and 42Ce have R4/2∼1.7 (light shells have Δj=2 pairs) while 134Te, 210Pb, 210Po have R4/2∼1.3 (in heavy nuclei the 1 circ s force lowers the open-quotes unique parityclose quotes state, leaving no Δj=2 pairs early in the shell). It also seems to account for the systematics of R4/2 in singly magic nuclei, and links the structure of pre-collective nuclei naturally onto the particle-hole RPA structure of vibrational modes
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Fall meeting of the Division of Nuclear Physics of the American Physical Society; Pacific Grove, CA (United States); 20-23 Oct 1993; CONF-931044--
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[en] Topics discussed in this International Summer School of Nuclear Physics include time dependent and Hartree-Fock methods in quantum mechanics and nuclear models; angular momentum, high spin states, giant resonance, nuclear deformation, collective model and excitations; nuclear molecules; heavy ion reactions; fission reactions; and inertial confinement
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1983; 521 p; World Scientific Pub. Co; Teaneck, NJ (USA); International summer school of nuclear physics; Brasov (Romania); 26 Aug - 7 Sep 1982; CONF-8208216--; ISBN 9971-950-69-3; 

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[en] An analysis of yrast energies in Collective medium and heavy even-even nuclei leads to two remarkable results. First, nuclei from Z=38-82 and with E(41+)/E(21+) ranging from 2.05 to 3.15 can be described by a generic anharmonic vibrator equation with nearly constant anharmonicity, independent of internal phonon structure. Secondly, the transition from anharmonic vibrator behavior to rotor can be cast as a critical phase transition with a critical point and a nuclear order parameter. These results suggest a need to reconsider the nature and evolution of nuclear structure, the universality of phonon and rotation-vibration interactions, and the manifestation of phase transitional behavior in finite-body nuclear systems
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Fall meeting of the Division of Nuclear Physics of the American Physical Society; Pacific Grove, CA (United States); 20-23 Oct 1993; CONF-931044--
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[en] The evolution of nuclear structure along the Xe and Ba isotopes with N<82 is studied in comparison with that in the Pt-Os isotopes and with interacting boson approximation calculations. As is well known, the Pt isotopes from 188-196Pt exhibit a stable structure very close to O(6), the lighter Pt isotopes and the Os nuclei evolve towards a rotor, and the heaviest Pt nuclei, 198,200Pt, show a tendency towards vibrational character. In contrast, we show that the Ba nuclei are best described by a trajectory from U(5) towards SU(3) that passes through an intermediate structure that resembles O(6) for N∼72 endash 76. The Xe appears to evolve from U(5) to O(6)-like. copyright 1998 The American Physical Society
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[en] Cross sections for the (p,t) reaction to ground states of even-even nuclei from Zr to Hg are interpreted in a simple approach. They are shown to be sensitive both to the degree of shell filling (which is related to the number of L=0 pairs in the ground state) and to the difference in the number of these pairs between target and final nuclei (that is, to the overlap of the initial and final systems). The cross sections separate according to the two broad classes of nuclei vibrational and rotational. The analysis is carried out in both a model-independent way and within the framework of the interacting boson approximation. copyright 1998 The American Physical Society
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[en] The properties of K=0+ excitations in deformed and transitional nuclei have recently been of intense interest. We present results of a study of the deexcitations of the lowest excited 0+ state in 152Sm from the ε-decay of 152Eu, yielding one of the few precisely known values of the branching ratio R0gγ=B(E2;2γ+→02+)/B(E2;2γ+→01+) =0.048(4), which is extraordinarily small. From T1/2(2γ+) we also obtain B(E2;2γ+→02+)=0.17 W.u. Values of R0gγ calculated in the interacting boson model (IBA) go to zero extremely rapidly, changing by orders of magnitude for a narrow range of parameter values. 152Sm is a rare case of a transitional nucleus that lands almost at the minimum. 152Sm and 154Gd are the only nuclei from 90≤N≤114 where the B(E2) values for all four transitions 2γ+→02+, 2γ+→01+, 02+→21+, and 21+→01+ are now known. In 152Sm these B(E2) values span three orders of magnitude, from 144 to 0.17 W.u. and are reproduced to within a factor of 2 endash 3 by the IBA. The rather strong B(E2;02+→21+) value of 33 W.u. suggest that the 02+ level is an example of a good low energy β-vibration. copyright 1998 The American Physical Society
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[en] Short communication
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Israel Atomic Energy Commission, Tel Aviv (Israel). Licensing Div; 206 p; Aug 1994; p. 62
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(c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
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[en] It was recently demonstrated that the empirical linear correlation of E(41+) with E(21+) is reproduced by the interacting boson model 1 (IBA-1) if a constant value for the coefficient κ of the Q·Q term is used. This constancy motivates the present investigation of whether it is possible to find sets of IBA-1 parameters, with fixed κ, that reproduce the data for a more general set of observables and a wide range of nuclei. A consistent procedure, based on contour plots of key observables, was used to extract ε and χ values for 145 nuclei spanning the Z = 50 endash 82 shell, which give reasonable overall agreement with the data with smoothly varying parameters. The constant κ constraint sometimes leads to parameter values different than normal: finite ε values (∼ 0.1 MeV) even for rotational nuclei and large χ values for transitional and vibrational nuclei that even increase towards the vibrational region. Finally, a systematic correlation of ε values with E(21+) was found. copyright 1997 The American Physical Society
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