Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session DG: Nuclear Structure: 110<A<150 |
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Chair: Joseph Hamilton, Vanderbilt University Room: Peralta |
Thursday, November 4, 2010 10:30AM - 10:42AM |
DG.00001: High-statistics study of the beta-decay of 110In Alejandra Diaz Varela, P.E. Garrett, G.C. Ball, J. Bangay, D. Cross, G.A. Demand, A.B. Garnsworthy, K.L. Green, G. Hackman, W.D. Kulp, K.G. Leach, C. Sumithrarachchi, C.E. Svensson, S. Triambak, J. Wong, J.L. Wood, S.W. Yates The stable even-even Cd isotopes have been considered excellent examples of vibrational nuclei, especially 110Cd and 112Cd. We have initiated a program at the TRIUMF-ISAC radioactive beam facility using the 8pi spectrometer and its associated auxiliary detectors to study these isotopes via high-statistics beta-decay measurements. To date, the decays of 112Ag/112In and 110In have been studied. The present work concentrates on the beta decay measurement of 110In to 110Cd. The data were collected in scaled-down gamma singles, gamma-gamma coincidence, and gamma-electron coincidence mode. A total of 850 million events have been sorted into a random-background subtracted gamma-gamma matrix. Details of the analysis to date will be reported. [Preview Abstract] |
Thursday, November 4, 2010 10:42AM - 10:54AM |
DG.00002: First identification of excited states in $^{114,115}$Rh Shaohua Liu, J.H. Hamilton, A.V. Ramayya, A. Gelberg, Y.X. Luo, J.K. Hwang, J.O. Rasmussen, S.J. Zhu Excited states in the very neutron-rich nuclei $^{114, 115}$Rh have been identified for the first time from a study of the prompt $\gamma$-rays emitted in the spontaneous fission of $^ {252}$Cf with the Gammasphere detector array. Eight levels with twelve transitions in the $\Delta I=1$ yrast band and five levels with eight transition in a side band in $^{114}$Rh are found. The level scheme is proposed to be built on $7^-$ excited state. The signature inversion of the yrast bands in $^ {106, 112, 114}$Rh are observed and the inversion point of $^ {114}$Rh is determined to be 10.6$\hbar$, which is smaller than 12.5$\hbar$ of $^{112}$Rh and 13.7$\hbar$ of $^{106}$Rh. Possible explanations will be presented. The level scheme of $^ {115}$Rh is established by observing eight levels with thirteen transitions in the yrast band and five levels with eight transition in a side band (yrare band). The existence of the large signature splitting and a yrare band in $^{115}$Rh shows features which are typical for triaxially deformed nuclei. Calculations based on the rigid-triaxial-rotor- plusquasiparticle model are performed to predict triaxiality with $\gamma =28^{\circ}$ for $^{115}$Rh. The results will be reported. [Preview Abstract] |
Thursday, November 4, 2010 10:54AM - 11:06AM |
DG.00003: Extended yrast level schemes in $^{121,123}$Cd W.B. Walters, C.J. Chiara New level structures for $^{121,123}$Cd will be presented that were determined in the study of the $^{64}$Ni- and $^{76}$Ge-induced fission of $^{238}$U at Gammasphere [1]. A number of transitions were previously observed by Hwang et al. from which yrast levels were identified with maximum proposed spins of 27/2- and 23/2- in $^{121,123}$Cd, respectively [2]. If the additional transitions have stretched E2 multipolarity, these level structures would be extended to 31/2- at 4083 keV, and 35/2- at 5365 keV in $^{121,123}$Cd, respectively. These level sequences will be compared to existing levels in the lighter odd-mass Cd nuclei and the isomeric structures and calculations in the heavier odd-mass Cd nuclei.\\[4pt] [1] C. J. Chiara, I. Stefanescu, A. A. Hecht, R. V. F. Janssens, W. B. Walters, R. Broda, M. P. Carpenter, B. Fornal, G. G\"{u}rdal, C. R. Hoffman, N. Hoteling, B. P. Kay, F. G. Kondev, W. Kr\'{o}las, T. Lauritsen, C. J. Lister, E. A. McCutchan, T. Pawlat, D. Seweryniak, N. Sharp, J. R. Stone, N. J. Stone, X. Wang, A. W\"{o}hr, J. Wrzesinski, S. Zhu, to be submitted for publication in Phys. Rev. C.\\[0pt] [2] J. K. Hwang et al., J. Phys. G: Nucl. Part. Phys. \textbf{28}, L9 (2002). [Preview Abstract] |
Thursday, November 4, 2010 11:06AM - 11:18AM |
DG.00004: Testing valence proton symmetry for Te and Cd Tan Ahn, Linus Bettermann, Robert Casperson, Raphael Chevrier, Andreas Heinz, Gabriela Ilie, David McCarthy, Desiree Radeck, Mallory Smith, Volker Werner, Elizabeth Williams To aid in the study of nuclei far from stability, various valence correlation schemes have been used to infer unknown properties of nuclei from known ones. One such valence correlation scheme is valence proton symmetry, which has been successfully tested for Xe and Pd pairs around the $Z = 50$ proton shell closure (Dewald 2008). To test the robustness of valence proton symmetry around mid-shell for the Te-Cd pairs, which is one proton pair closer to $Z = 50$, we measured the lifetimes of the $2^+_1$ level in $^{116}$Te and $^{118}$Te using the Recoil Distance Doppler Shift method. The results of this experiment will be presented. \\[4pt] A. Dewald et al. Phys. Rev. C 78, 051302 (2008) [Preview Abstract] |
Thursday, November 4, 2010 11:18AM - 11:30AM |
DG.00005: Study of the ($d$,$p$) reaction on $^{130,136}$Xe in inversve kinematics B.P. Kay, J.P. Schiffer, B.B. Back, S.I. Baker, J.A. Clark, C.M. Deibel, C.R. Hoffman, K.E. Rehm, S.J. Freeman, A.M. Howard, D.K. Sharp, J.S. Thomas, S. Bedoor, J.C. Lighthall, S.T. Marley, D.V. Shetty, A.H. Wuosmaa, T. Bloxham We used the HELIOS spectrometer at Argonne National Laboratory to study the neutron-adding ($d$,$p$) reaction on $^{130,136}$Xe, in inverse kinematics. Of interest is the evolution of single-particle strength across the $N=82$ isotones in the case of $^{136}$Xe, and nuclear structure relevant to the neutrinoless double beta decay matrix elements in the case of $^{130}$Xe. A beam energy of 10 MeV/u was used for each Xe isotope with typical beam intensities of 0.1 pnA. The targets used were $\sim$150-$\mu$g/cm$^{2}$ thick CD$_{2}$. In both instances, an excitation-energy resolution of better than 100 keV was obtained in the outgoing proton spectra. Absolute cross sections were extracted via a simultaneous monitoring of target luminosity at small angles that takes into account in-beam degradation of the target. Angular distributions and spectroscopic factors will be presented. This work was supported by the US Department of Energy, Office of Nuclear Physics, under Contract Nos. DE-AC02-06CH11357 and DE-FG02-04ER41320, NSF Grant No. PHY-08022648, and the UK Science and Technology Facilities Council. [Preview Abstract] |
Thursday, November 4, 2010 11:30AM - 11:42AM |
DG.00006: Low-lying Structure of $^{134}$Xe from Inelastic Neutron Scattering E.E. Peters, B.P. Crider, S.F. Ashley, M.T. McEllistrem, S.W. Yates Unlike the transition from spherical vibrators to axially symmetric rotors, little is known about the transition from spherical vibrators to gamma-soft nuclei. The stable isotopes of xenon span a region which exhibits this lesser understood shape transition. While $^{136}$Xe shows evidence of being a spherical vibrator, the lighter xenon nuclei demonstrate gamma-soft behavior. Measurements to determine the nuclear structure of the xenon isotopes are difficult, however, since they are gases under ambient conditions, and solid targets are much more amenable to typical methods. Recently, highly enriched $(>99.9\%)$ samples of $^{132}$Xe and $^{134}$Xe were converted to solid XeF$_{2}$. These isotopes were studied at the University of Kentucky 7-MV Van de Graaff accelerator facility using the inelastic neutron scattering reaction with gamma-ray detection. Both excitation function and angular distribution data were obtained for the low-lying levels. First results of the experiments on $^{134}$Xe will be presented. [Preview Abstract] |
Thursday, November 4, 2010 11:42AM - 11:54AM |
DG.00007: Coulomb Excitation of $^{124,126,128}$Sn(Z=50) on $^{12}$C, $^{27}$Al, and $^{50}$Ti: Approaching the N=82 Shell Closure via N=74,76,78 J.M. Allmond, D.C. Radford, C. Baktash, J.C. Batchelder, A. Galindo-Uribarri, C.J. Gross, P.A. Hausladen, K. Lagergren, Y. Larochelle, E. Padilla-Rodal, C.-H. Yu The determination of $<$0$_{1}\vert \vert $E2$\vert \vert $2$_{1}>$ matrix elements from the Coulomb excitation of $^{124,126,128}$Sn(Z=50) on a $^{12}$C target is presented. Furthermore, preliminary results are presented for the Coulomb excitation of $^{124,126,128}$Sn on $^{27}$Al and $^{50}$Ti targets, which, combined with the results from the $^{12}$C target, can provide an upper/lower limit for the 2$_{1}^{+}$ static quadrupole moments, Q(2$_{1})$ = 0.758 x $<$2$_{1}\vert \vert $E2$\vert \vert $2$_{1}>$ (expected to be $\approx $ 0). Indeed, accurate knowledge of 2$_{1}^{+}$ systematics, i.e., E(2$_{1})$, $<$0$_{1}\vert \vert $E2$\vert \vert $2$_{1}>$, and $<$2$_{1}\vert \vert $E2$\vert \vert $2$_{1}>$, are essential for testing consistency in models (e.g., deformation) at and near the neutron-rich N=82 shell closure. [Preview Abstract] |
Thursday, November 4, 2010 11:54AM - 12:06PM |
DG.00008: Octupole Deformation in 143-146 Barium N.T. Brewer, W.A. Yzaguirre, J.H. Hamilton, S.H. Liu, A.V. Ramayya, J.K. Hwang, C. Goodin, J.O. Rasmussen, S.J. Zhu, Y.X. Luo, G.M. Ter-Akopian, A.V. Daniel, Y. Oganessian Nuclei produced in the fission of $^{252}$Cf at Lawrence Berkeley National Lab and measured using the Gammasphere array continue to give insight into neutron rich nuclei. Using our high statistics data, we have reexamined high-spin states and linking transitions associated with octupole deformation in 143-146 Ba. Quadrupole/octupole-mixed-deformation is characterized by two $\Delta $I=1 rotational level bands which are doublets with opposite parities. This is modeled by the simplex quantum number s= $\pm $1 or s= $\pm $i. In $^{143}$Ba, the s= -i levels are extended to 43/2$^{+}$ with a total of six new levels that are discovered along with three new linking transitions consistent with octupole deformation. In $^{144}$Ba, two new levels on top of the s= +1 doublet and one new level with 12 new linking transitions are found to give better evidence for an s= -1 doublet band than was previously reported. Six new levels found in $^{145}$Ba along with two linking transitions extend the s= +i band up to 41/2$^{+}$. The theoretically explained weakening of E1 transition strength in $^{146}$Ba for high-spin states are now re-measured with lower upper limits on the intensities of the E1 transitions. [Preview Abstract] |
Thursday, November 4, 2010 12:06PM - 12:18PM |
DG.00009: Nuclear Dipole Resonance in N = 82 Nuclei A.P. Tonchev, S.L. Hammond, J.H. Kelley, E. Kwan, H. Lenske, R. Raut, G. Rusev, W. Tornow, N. Tsoneva In stable and weakly bound neutron-rich nuclei, a resonance-like concentration of dipole states has been observed for excitation energies around the neutron separation energy. This clustering of strong dipole states has been named the pygmy dipole resonance (PDR) in contrast to the giant dipole resonance that dominates the E1 response. High-sensitivity studies of E1 and M1 transitions in N = 82 nuclei using the nearly monoenergetic and 100{\%} linearly-polarized photon beams from TUNL's High-Intensity-Gamma-Ray Source facility will be presented. The nuclear dipole-strength distribution of the PDR has been measured and novel information about the character of this mode of excitation has been obtained. The data will be compared to calculations using statistical and quasiparticle random-phase approximation methods. [Preview Abstract] |
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