We report on the first observation of a set of identical, dynamical moments of inertia within the... more We report on the first observation of a set of identical, dynamical moments of inertia within the same nucleus corresponding to different quanta of vibrational phonons, The examples shown are those of y and ~r,, vibrations in the deformed rare-earth region of nuclei. It is suggested that the determination of dynamical moments of inertia may be a signature of multi-phonon vibrational bands in deformed nuclei everywhere in the chart of nuclides.
Transition from Collective to Noncollective Rotation at High Spin in N= 87 Nuclei
... Szymanski, Phys. Lett. 102B, 235 (1981). 225 Page 246. CYRUS BAKTASH 18. C. Baktash, IY Loc, ... more ... Szymanski, Phys. Lett. 102B, 235 (1981). 225 Page 246. CYRUS BAKTASH 18. C. Baktash, IY Loc, FK McGowan, LL Riedln^ er, MP Fev; oll and NR Johnson (to be published). 19. T. Dossing, Phys. Scrlpta 29, 258 (1981). 20. C ...
Charged particles as probes to study entrance channel effects in the composite system {sup 164} Yb
We present preliminary results in a study of entrance channel effects by comparing measured charg... more We present preliminary results in a study of entrance channel effects by comparing measured charged particles and γ-ray multiplicities in coincidence with residue nuclei (identified by discrete transitions) from both mass symmetric and symmetric reactions. The systems studiede are â¶â´Ni + ¹°°Mo and ¹â´â¸Sm, both of which would produce the ¹â¶â´Yb compound nucleus with 52 MeV of excitation energy. In the (α2n) exit channel, the center of mass α-particle angular distribution is symmetric around 90° in the Ni-induced reaction, indicating emission from a fully equilibrated system. Furthermore, the extracted anisotropies show no evidence for an enhancement of α-particle emission in the low energy region, which indicates emission from a nearly spherical system. However, the corresponding angular distribution of the ¹â¶O-induced reaction shows a strong forward component, which is a clear signature of a non-statistical contribution to the residue cross-section. This non-statistical component has to be taken into account when comparing decay modes of a compound nucleus formed in different entrance channels.
The ORNL radioactive ion beam project with the ORIC accelerator
ABSTRACT The ORNL project to produce medium-intensity, proton-rich, radioactive ion beams (RIBS) ... more ABSTRACT The ORNL project to produce medium-intensity, proton-rich, radioactive ion beams (RIBS) for astrophysics, nuclear physics, and applied research with the Holifield Heavy Ion Research Facility (HHIRF) accelerators has been approved. Radioactive atoms will be produced by fusion reactions in an Isotope Separator On-Line (ISOL) type target-ion source assembly using light ion beams from the Oak Ridge Isochronous Cyclotron (ORIC). The radioactive atoms will be converted to negative ions using either (1) direct-surface ionization, or (2) charge exchange following positive ionization. After acceleration to approximately 300 keV from a high-voltage platform, these negative ions will be injected into the 25-MV tandem accelerator for acceleration to higher energies. Beams of up to mass 80 will be accelerated to energies greater than 5 MeV/nucleon. For some radioactive beams. intensities greater than I pnA are possible.
A new island of superdeformed nuclei with major-to-minor axis ratio of 2: 1 has recently been dis... more A new island of superdeformed nuclei with major-to-minor axis ratio of 2: 1 has recently been discovered in the A-SO medium-mass region, confirming the predictions for the existence of a large SD gap at particle number N,Z-44. The general properties of more than 20 bands observed so far will be reviewed here, and compared with those of the superdeformed bands in the heavier nuclei. 'The submitted manuscript has been authored by a contractor d the US. Government under contra! No. DE-AC05-960R22464. Accordingly the U.S. Government retains a' nonkclusive. royalty-free license lo publish or reproduce the puMished form of this contribution. or allow others to do so, for US. Government purposes.'-DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied. or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, m mmendirtion, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Spherical and Superdeformed Structures Near Doubly-Magic Nuclei^ 40Ca,^ 56Ni, and^ 100Sn
For more than thirty years, shell model calculations have predicted that multiparticle-multihole ... more For more than thirty years, shell model calculations have predicted that multiparticle-multihole excitations across magic numbers 8, 20 and 28 would lead to very deformed and superdeformed states in the vicinity of doubly-magic nuclei ^16O, ^40Ca, and ^16Ni. These expectations were later confirmed in various cluster and mean field calculations that predicted the existence of new islands of superdeformation centered around ^32S and ^60Zn. However, it was only recently that advances in detector technology have allowed exploration of these weakly-populated structures. In this talk, I will present results of our recent experiments that have succeeded in identifying these long-sought states and their exotic decay modes. These data have provided a unique testing ground to confront, compare, and relate state-of-the-art calculations in the framework of microscopic (large-scale shell models, Quantum Monte Carlo Diagonalization), and mean field theories. Highlights of these results, including a discussion of the importance of neutron-proton pairing correlations in these nearly N=Z nuclei will be discussed. * Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
We report on the first observation of a set of identical, dynamical moments of inertia within the... more We report on the first observation of a set of identical, dynamical moments of inertia within the same nucleus corresponding to different quanta of vibrational phonons, The examples shown are those of y and ~r,, vibrations in the deformed rare-earth region of nuclei. It is suggested that the determination of dynamical moments of inertia may be a signature of multi-phonon vibrational bands in deformed nuclei everywhere in the chart of nuclides.
Transition from Collective to Noncollective Rotation at High Spin in N= 87 Nuclei
... Szymanski, Phys. Lett. 102B, 235 (1981). 225 Page 246. CYRUS BAKTASH 18. C. Baktash, IY Loc, ... more ... Szymanski, Phys. Lett. 102B, 235 (1981). 225 Page 246. CYRUS BAKTASH 18. C. Baktash, IY Loc, FK McGowan, LL Riedln^ er, MP Fev; oll and NR Johnson (to be published). 19. T. Dossing, Phys. Scrlpta 29, 258 (1981). 20. C ...
Charged particles as probes to study entrance channel effects in the composite system {sup 164} Yb
We present preliminary results in a study of entrance channel effects by comparing measured charg... more We present preliminary results in a study of entrance channel effects by comparing measured charged particles and γ-ray multiplicities in coincidence with residue nuclei (identified by discrete transitions) from both mass symmetric and symmetric reactions. The systems studiede are â¶â´Ni + ¹°°Mo and ¹â´â¸Sm, both of which would produce the ¹â¶â´Yb compound nucleus with 52 MeV of excitation energy. In the (α2n) exit channel, the center of mass α-particle angular distribution is symmetric around 90° in the Ni-induced reaction, indicating emission from a fully equilibrated system. Furthermore, the extracted anisotropies show no evidence for an enhancement of α-particle emission in the low energy region, which indicates emission from a nearly spherical system. However, the corresponding angular distribution of the ¹â¶O-induced reaction shows a strong forward component, which is a clear signature of a non-statistical contribution to the residue cross-section. This non-statistical component has to be taken into account when comparing decay modes of a compound nucleus formed in different entrance channels.
The ORNL radioactive ion beam project with the ORIC accelerator
ABSTRACT The ORNL project to produce medium-intensity, proton-rich, radioactive ion beams (RIBS) ... more ABSTRACT The ORNL project to produce medium-intensity, proton-rich, radioactive ion beams (RIBS) for astrophysics, nuclear physics, and applied research with the Holifield Heavy Ion Research Facility (HHIRF) accelerators has been approved. Radioactive atoms will be produced by fusion reactions in an Isotope Separator On-Line (ISOL) type target-ion source assembly using light ion beams from the Oak Ridge Isochronous Cyclotron (ORIC). The radioactive atoms will be converted to negative ions using either (1) direct-surface ionization, or (2) charge exchange following positive ionization. After acceleration to approximately 300 keV from a high-voltage platform, these negative ions will be injected into the 25-MV tandem accelerator for acceleration to higher energies. Beams of up to mass 80 will be accelerated to energies greater than 5 MeV/nucleon. For some radioactive beams. intensities greater than I pnA are possible.
A new island of superdeformed nuclei with major-to-minor axis ratio of 2: 1 has recently been dis... more A new island of superdeformed nuclei with major-to-minor axis ratio of 2: 1 has recently been discovered in the A-SO medium-mass region, confirming the predictions for the existence of a large SD gap at particle number N,Z-44. The general properties of more than 20 bands observed so far will be reviewed here, and compared with those of the superdeformed bands in the heavier nuclei. 'The submitted manuscript has been authored by a contractor d the US. Government under contra! No. DE-AC05-960R22464. Accordingly the U.S. Government retains a' nonkclusive. royalty-free license lo publish or reproduce the puMished form of this contribution. or allow others to do so, for US. Government purposes.'-DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied. or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, m mmendirtion, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Spherical and Superdeformed Structures Near Doubly-Magic Nuclei^ 40Ca,^ 56Ni, and^ 100Sn
For more than thirty years, shell model calculations have predicted that multiparticle-multihole ... more For more than thirty years, shell model calculations have predicted that multiparticle-multihole excitations across magic numbers 8, 20 and 28 would lead to very deformed and superdeformed states in the vicinity of doubly-magic nuclei ^16O, ^40Ca, and ^16Ni. These expectations were later confirmed in various cluster and mean field calculations that predicted the existence of new islands of superdeformation centered around ^32S and ^60Zn. However, it was only recently that advances in detector technology have allowed exploration of these weakly-populated structures. In this talk, I will present results of our recent experiments that have succeeded in identifying these long-sought states and their exotic decay modes. These data have provided a unique testing ground to confront, compare, and relate state-of-the-art calculations in the framework of microscopic (large-scale shell models, Quantum Monte Carlo Diagonalization), and mean field theories. Highlights of these results, including a discussion of the importance of neutron-proton pairing correlations in these nearly N=Z nuclei will be discussed. * Managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
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