Showing papers by "R. F. Casten published in 2000"
TL;DR: Evidence for the first empirical example of a transitional dynamical symmetry at a critical point is discussed in the spectrum of 134Ba and the role of such classes of symmetries in nuclear structural evolution is discussed.
Abstract: Evidence for the first empirical example of a transitional dynamical symmetry at a critical point is discussed in the spectrum of ${}^{134}\mathrm{Ba}$. The role of such classes of symmetries in nuclear structural evolution is also discussed.
207 citations
TL;DR: Exotic nuclei are known to exhibit qualitatively new phenomena and provide a new testing ground for our understanding of quantum many-body science as discussed by the authors, and they have been extensively studied in the literature.
60 citations
TL;DR: In this article, shape invariants for the ground state, formed by quadrupole moments up to sixth order, are studied in the dynamical symmetry limits and over the whole structural range of the interacting boson model.
Abstract: In terms of the interacting boson model (IBM), shape invariants for the ground state, formed by quadrupole moments up to sixth order, are studied in the dynamical symmetry limits and over the whole structural range of the IBM-1. The results are related to the effective deformation parameters and their fluctuations in the geometrical model. New signatures that can distinguish vibrator and {gamma}-soft rotor structures, and one that is related to shape coexistence, are identified. (c) 2000 The American Physical Society.
45 citations
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01 Oct 2000-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The Yale Rochester Array for SpecTroscopy (YRAST Ball) as mentioned in this paper is a state-of-the-art c-ray spectroscopy array with up to 30 Compton suppressed Ge detectors.
Abstract: The Yale Rochester Array for SpecTroscopy, YRAST Ball, is described. Containing up to 30 Compton suppressed Ge detectors YRAST Ball is a powerful new array for c-ray spectroscopy. Several of its auxiliary detectors, including a multi-element solar cell array for heavy charged fragment detection and a new state of the art plunger system for recoil distance measurements are also described. ( 2000 Elsevier Science B.V. All rights reserved.
34 citations
TL;DR: Both exact and approximate expressions are shown to reflect and support recent discussions of phase coexistence and β -softness in 152 Sm by applying them to the yrast states, and for the first time, to an excited family of levels based on the 0 + 2 level as well.
21 citations
TL;DR: In this paper, the negative-parity level scheme was investigated in connection with its description within the framework of an extended supersymmetry, and two weakly connected level structures, built on the 2(-) ground state and on the 5(+) isomer at 84.7 keV, were observed.
Abstract: Excited states in (196)AU, populated in the Pt-196(p,n) and (d,2n) reactions, were investigated by in-beam gamma -ray and conversion-electron spectroscopy. Two only weakly connected level structures, built on the 2(-) ground state (negative-parity level scheme) and on the 5(+) isomer at 84.7 keV (positive-parity level scheme), are observed. The point of main effort of the present work was the investigation of the negative-parity level scheme in connection with its description within the framework of an extended supersymmetry. For this level scheme we observe 25 excited states up to an excitation energy of 500 keV, of which 23 had already been identified in a recent study of (196)AU by transfer reactions. From 500 to 800 keV we observe 28 additional levels compared to 20 levels observed in the transfer reactions. The excitation energies derived in the studies of the (p,n) compound reaction and the (p,d) transfer reaction agree within 1 keV, and the complementary information obtained from the two reactions led to improved spin determinations. The negative-parity level structure is compared with the predictions of the extended supersymmetry. (Less)
20 citations
TL;DR: The N(p)N(n) scheme, which has been extensively applied to even-even nuclei, is found to be a very good benchmark for odd-even, even-odd, and doubly-odd nuclei as well.
Abstract: The ${N}_{p}{N}_{n}$ scheme, which has been extensively applied to even-even nuclei, is found to be a very good benchmark for odd-even, even-odd, and doubly-odd nuclei as well. There are no apparent shifts in the correlations for these four classes of nuclei. The compact correlations highlight the deviant behavior of the $Z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}78$ nuclei and are used to deduce effective valence proton numbers near $Z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}64$ as well as to study the evolution of the $Z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}64$ subshell gap.
18 citations
01 Jan 2000
TL;DR: Exotic nuclei are known to exhibit qualitatively new phenomena and provide a new testing ground for our understanding of quantum many-body science as mentioned in this paper, and they have been extensively studied in the literature.
Abstract: The quantum many body system of protons and neutrons that makes up the nucleus of atoms has been studied for nearly 100 years, yet there are many unexplored aspects. One of the frontiers is in the production and study of isotopes with exotic neutron to proton number ratios. A key technical development that allows the study of exotic nuclei is the capability to produce them as beams. Exotic nuclei are known to exhibit qualitatively new phenomena and provide a new testing ground for our understanding of quantum many-body science. This article outlines some of the new aspects of exotic nuclei, how they are produced, and how they are studied. A description is given of how one recognizes the signatures of exotic nuclei and how manifestations of changes in the standard structure of nuclei may be identified.
4 citations
TL;DR: In this article, a level scheme was developed containing levels grouped into 23 rotational bands below 1 MeV, of which six bands are new and several others, known previously, have been modified and expanded based upon their experimental data.
Abstract: The nucleus ${}^{166}\mathrm{Ho}$ was studied with thermal and average resonance neutron capture and with $(d,p)$ and ${(d,}^{3}\mathrm{He})$ reactions. We have devoted a large effort to the measurements of $\ensuremath{\gamma}\ensuremath{\gamma}$-coincidence spectra in the broad energy interval 50\char21{}6243 keV. From these data and those of previous studies, the level scheme has been developed containing levels grouped into 23 rotational bands below 1 MeV. Of these, six bands are new and several others, known previously, have been modified and expanded based upon our experimental data. In all, 32 new levels have been identified. Of particular note has been the identification of two rotational bands whose underlying structure consists of $\ensuremath{\gamma}$-vibrational states built upon the two lowest energy quasiparticle states in ${}^{166}\mathrm{Ho}.$ Two new Gallagher-Moszkowski matrix elements were determined: ${E}_{\mathrm{GM}}{(p7/2}^{\ensuremath{-}}[523]\ifmmode\pm\else\textpm\fi{}{n5/2}^{\ensuremath{-}}[523])=\ensuremath{-}108.5$ keV and ${E}_{\mathrm{GM}}{{(p7/2}^{\ensuremath{-}}[523]\ifmmode\pm\else\textpm\fi{}{n7/2}^{+}[633])\ensuremath{\mp}{Q}_{22}}=+138.2$ keV. The resultant level scheme is in good agreement with semiempirical and quasiparticle phonon models where residual interactions have been taken into account. Suggestions are given for further experimentation on ${}^{166}\mathrm{Ho}$ level structure using existing technology.
4 citations
TL;DR: In this article, different classes of evolutionary tracks in nuclear spherical-deformed transition regions are discussed and the usefulness of this morphological classification for the study of exotic nuclei is stressed.
2 citations
TL;DR: In this article, a superdeformed ridge with a separation of Delta E-gamma=52 keV with a total intensity of 1.8+/-0.5% that of Dy-150 has been observed.
Abstract: An experiment has been performed to search for superdeformed (SD) states in Dy-149,Dy-150. While no evidence for discrete superdeformed states has been observed, a superdeformed ridge with a separation of Delta E-gamma=52 keV with a total intensity of 1.8+/-0.5% that of Dy-150 has been observed. An upper limit of 0.8% (0.9%), of the intensity of Dy-150 (Dy-149), is placed for observation of the most intense discrete line states. The relative weakness in the SD population is suggested to be due to a rapid decrease in the depth of the superdeformed minimum, as one moves away from doubly magic Dy-152.
TL;DR: In this article, the Wright Nuclear Structure Laboratory at Yale presented a model of the Wright nuclear structure and showed that it can be used to construct a nuclear structure from a single atom.
Abstract: (2000). The Wright Nuclear Structure Laboratory at Yale. Nuclear Physics News: Vol. 10, No. 2, pp. 4-11.