C. H. Yu

Structure Of Rare-Earth Nuclei Around The Proton Drip Line

Decay studies on rare earth nuclei around the proton drip line have been performed by means of the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility in Oak Ridge. The proton emission from the odd‐odd N=77 isotone 146Tm was reinvestigated, resulting in the assignment of the 1.01 MeV proton line to the decay of a short‐lived 146Tm state. A new proton radioactivity of 144Tm was identified. The decays of isomeric levels in the N=77 isotones, 140Eu, 142Tb and 144Ho were remeasured using γ and electron detectors. The analysis of the structure of studied nuclei, which accounts for the coupling between the protons and neutrons and for core excitations, is presented.

Forking and Unusual Decay Out of Superdeformed Bands in 83Zr

Two superdeformed (SD) bands extending over eight to eleven transitions have been identified in Zr-83, The quadrupole moment of the more intense band was determined by the Residual Doppler Shift Method and is consistent with a quadrupole deformation of beta(2) approximate to 0.5. The large quadrupole moment and population intensity of the yrast SD band (approximate to 5%) in Zr isotopes relative to their isotones in Sr and Y nuclei suggest the presence of a large SD shell gap at proton number Z = 40, At the decay-out points, the Routhians of the SD bands reapproach that of the positive parity normally-deformed states which may be the reason why both of these bands feed mainly (approximate to 85%) into the positive-parity yrast band.

High-precision B(E2) measurements of semi-magic Ni 58,60,62,64 by Coulomb excitation

J. M. Allmond,1 B. A. Brown,2,3 A. E. Stuchbery,4 A. Galindo-Uribarri,5,6 E. Padilla-Rodal,7 D. C. Radford,5 J. C. Batchelder,8 M. E. Howard,9 J. F. Liang,5 B. Manning,9 R. L. Varner,5 and C.-H. Yu5 1JINPA, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 2National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA 3Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA 4Department of Nuclear Physics, Australian National University, Canberra ACT 0200, Australia 5Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA 6Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA 7Instituto de Ciencias Nucleares, UNAM, AP 70-543, 04510 Mexico, D.F., Mexico 8UNIRIB, Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA 9Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08903, USA (Received 13 May 2014; revised manuscript received 7 August 2014; published 15 September 2014)

Superdeformed Bands in 80Sr and the Evolution of Deformation in Sr Isotopes

Four superdeformed bands are reported in Sr-80, extending known superdeformation in the Sr-38 series down to N = 42. The characteristics of these bands are discussed. Residual Doppler shifts were measured and average transition quadrupole moments (Q(t)) inferred for these new bands, These Q(t) values are compared to Q(t) values obtained for previously identified superdeformed bands in Sr81-83. The low Q(t) of 2.7(-0.6)(+0.7) eb obtained for the yrast band in Sr-80 indicates a reduction in the deformation of yrast superdeformed bands in the series Sr80-83 with decreasing N, and possibly the onset of triaxiality in superdeformed shapes

Electromagnetic Moments of Radioactive 136Te and the Emergence of Collectivity 2p ⊕ 2n outside of Double-Magic 132Sn

Radioactive ^{136}Te has two valence protons and two valence neutrons outside of the ^{132}Sn double shell closure, providing a simple laboratory for exploring the emergence of collectivity and nucleon-nucleon interactions. Coulomb excitation of ^{136}Te on a titanium target was utilized to determine an extensive set of electromagnetic moments for the three lowest-lying states, including B(E2;0_{1}^{+}→2_{1}^{+}), Q(2_{1}^{+}), and g(2_{1}^{+}). The results indicate that the first-excited state, 2_{1}^{+}, composed of the simple 2p⊕2n system, is prolate deformed, and its wave function is dominated by excited valence neutron configurations, but not to the extent previously suggested. It is demonstrated that extreme sensitivity of g(2_{1}^{+}) to the proton and neutron contributions to the wave function provides unique insight into the nature of emerging collectivity, and g(2_{1}^{+}) was used to differentiate among several state-of-the-art theoretical calculations. Our results are best described by the most recent shell model calculations.

100 Sn core excitations in 102 In

Nuclei in the vicinity of the doubly-magic Sn-100 nucleus have been studied, and an extended level scheme for In-102 has been established. The level structure comprises both the negative parity states involving the nuh(11/2) orbital, and levels due to the breakup of the doubly-magic Sn-100 core. Results of a large-scale shell model calculation, using realistic and empirical effective interactions with Sr-88 as a core, are in very good agreement with the experimental data.

Fine structure in proton emission

Deformations and wave functions of proton‐radioactive nuclei are studied using measured fine structure properties of proton emission and microscopic theoretical models. The experimental data are available for 131Eu and 145Tm decays, as well as for 141gsHo, where an observation of fine structure in proton emission is reported for the first time.

Fine structure in proton emission from the deformed 141g.sHo 141mHo

Fine structure in proton emission from the deformed states 141g.s.Ho (T1/2 = 4.1 ms) and 141mHo (T1/2 = 7.4 μs) has been discovered at Oak Ridge by detecting fusion evaporation residues with the Recoil Mass Spectrometer, Si‐detectors and digital signal processing electronics. The branching ratios to the first 2+ excited state in 140Dy were measured to be Ipg.s.(2+) = 0.9±0.1% and Ipm(2+) = 1.7±0.5%. A comparison of the available calculations to the experimental values calls for further development of the theoretical models.

On the origin of low-lying M1 strength in even-even nuclei

The 2+2 state in 132Te is identified as the one-phonon MSS in a projectile Coulomb excitation experiment presenting a firm example of a MSS in unstable, neutron rich nuclei. The results of shell-model calculations based on the low-momentum interaction Vlow−k are in good agreement with experiment demonstrating, the ability of the effective shell-model interaction to produce states of mixed symmetry character.

One-phonon isovector 2 + 1,MS state in the neutron rich nucleus 132 Te

The 2{sub 2}{sup +} state in {sup 132}Te is identified as the one-phonon mixed-symmetry state in a projectile Coulomb excitation experiment presenting a firm example of a mixed-symmetry state in unstable, neutron-rich nuclei. The results of shell-model calculations based on the low-momentum interaction V{sub low-k} are in good agreement with experiment demonstrating the ability of the effective shell-model interaction to produce states of mixed-symmetry character.