Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session HE: Nuclear Structure IV |
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Chair: Torben Lauritsen, Argonne National Laboratory Room: 103AB |
Friday, October 28, 2011 10:30AM - 10:42AM |
HE.00001: Possible excited deformed rotational bands in $^{82}$Ge J.K. Hwang, J.H. Hamilton, A.V. Ramayya, N.T. Brewer, Y.X. Luo, J.O. Rasmussen, S.J. Zhu Excited states of neutron-rich nucleus $^{82}$Ge were studied from the spontaneous fission of $^{252}$Cf. Eleven new transitions and seven new levels in $^{82}$Ge were identified by using X(Dy)-$\gamma -\gamma $ and $\gamma -\gamma -\gamma $ triple coincidences. Possible excited deformed rotational bands are observed, for the first time, in this nuclear region. Coexistence of the spherical ground and deformed excited shapes is proposed in $^{82}$Ge. These deformed rotational bands can be formed by 2-particle, 2-hole excitations with 0$^{+}$ pairing energy of $\nu $9/2[404]$^{-2}$x1/2[431]$^{2}$ across the N=50 closed shell. [Preview Abstract] |
Friday, October 28, 2011 10:42AM - 10:54AM |
HE.00002: Band Structures in $^{230}$Th R.V.F. Janssens, S. Zhu, M.P. Carpenter, I. Ahmad, C.R. Hoffman, T.L. Khoo, B.P. Kay, F.G. Kondev, T. Lauritsen, C.J. Lister, E.A. Ricard-McCutchan, D. Seweryniak, Y. Toh, D. Ayangeakaa, S. Frauendorf, U. Garg, D. Patel, J. Matta, W. Reviol, D.G. Sarantites, X. Wang, S. Lalkovski Experimental evidence for the recently proposed phenomenon of condensation of rotational-aligned octupole phonons [1] has been observed in $^{240}$Pu [2] and $^{238}$U [3]. In order to study this phenomenon in $^{230}$Th, an experiment has been carried out at ATLAS. The octupole band was extended up to spin 29. In addition, three positive-parity bands were observed for the first time. With increasing spin, the octupole band and the ground state band (gsb) start forming a smooth sequence of states with alternating spin and parity. Furthermore, the Routhian of the octupole band becomes lower than that of the gsb at rotational frequencies above 0.24 MeV. A band built on the second 0$^+$ state at 567 keV was discovered in this experiment, but it decays only to the gsb. [1] S. Frauendorf, Phys. Rev. C 77, 021304(R) (2008), [2] X. Wang et al., Phys. Rev. Lett. 102, 122501 (2009), [3] S. Zhu et al., Phys. Rev. C 81, 041306(R) (2010). This work was supported by DOE, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357. [Preview Abstract] |
Friday, October 28, 2011 10:54AM - 11:06AM |
HE.00003: Level structure of $^{67}$Ni and the nature of yrast excitations near N=40 S. Zhu, R.V.F. Janssens, M.P. Carpenter, T. Lauritsen, D. Seweryniak, X. Wang, C.J. Chiara, W.B. Walters, N. Hoteling, I. Stefanescu, J.R. Stone, R. Broda, B. Fornal, W. Krolas, T. Pawlat, J. Wrzesinski The region of nuclei around $^{68}$Ni$_{40}$, with its closed proton shell and closed neutron harmonic-oscillator sub-shell, continues to be of much interest as recent data indicate the stabilizing effects of the N=40 gap are rather localized in N and Z. With a single neutron hole in $^{68}$Ni, the structure of $^{67}$Ni provides an opportunity for detailed comparisons with calculations using different effective interactions and for learning about the nature of the yrast excitations. A level scheme built on the previously known 13-$\mu$s isomer has been delineated up to an excitation energy of ~5.3 MeV and a spin of 21/2. Shell model calculations have been carried out using two effective interactions in the $f_{5/2}pg_{9/2}$ model space with $^{56}$Ni as a core. Satisfactory agreement between experiment and theory is achieved. Comparisons between experiment and calculations indicate that the yrast and near-yrast excitations are dominated by complex multi-particle-hole excitations. This work is supported in part by the U.S. DOE, Office of Nuclear Physics under contracts DE-AC02-06CH11357 and DE-FG02-94-ER40834. [Preview Abstract] |
Friday, October 28, 2011 11:06AM - 11:18AM |
HE.00004: High-spin states in $^{118,120}$Sn above the 10$^{+}$ isomers. N. Fotiades, M. Devlin, R.O. Nelson, J.A. Cizewski, R. Krucken, R.M. Clark, P. Fallon, I.Y. Lee, A.O. Macchiavelli, W. Younes High-spin states in $^{118}$Sn and $^{120}$Sn were studied via prompt $\gamma$-ray spectroscopy. The data were obtained in three Gammasphere experiments at LBNL with reactions populating both isotopes as fission fragments following fission of much heavier compound nuclei. Additional data were obtained in a GEANIE experiment at LANL where the isotopes were populated as evaporation residues in the $^{124}$Sn$(n,xn\gamma)$, with $x=5,7$, reactions. Sequences of transitions were observed for the first time feeding the previously known 10$^{+}$ isomers, at 3108-, and 2902-keV excitation energy, and with 2.5$\mu$s and 6.26$\mu$s half-life, for $^{118}$Sn and $^{120}$Sn, respectively. The level schemes above the isomers were established up to 6646-, and 5673-keV excitation energy, for $^{118}$Sn and $^{120}$Sn, respectively. The experimental results are compared with predictions from shell-model calculations. [Preview Abstract] |
Friday, October 28, 2011 11:18AM - 11:30AM |
HE.00005: First identification of high-spin states in $^{152}$Pr Shaohua Liu, J.H. Hamilton, A.V. Ramayya, J.K. Hwang, N.T. Brewer, S. Yue, F.R. Xu, Y.X. Luo, J.O. Rasmussen, S.J. Zhu, W.C. Ma The odd-odd neutron-rich nucleus $^{152}$Pr has been studied from the spontaneous fission of $^{252}$Cf with the Gammasphere detector array at Lawrence Berkeley National Laboratory. A high-spin level scheme of $^{152}$Pr has been established for the first time. Angular correlation and internal conversion coefficient measurements are used to determine level spins and parities in the yrast band of $^{152}$Pr relative to the band head. The possible configurations of the band head have been discussed based on systematics and total Routhian surface calculations. The results will be presented. [Preview Abstract] |
Friday, October 28, 2011 11:30AM - 11:42AM |
HE.00006: Investigating High Spin States in Transplutonium nuclei with Ultimate Cranker Y. Qiu, P. Chowdhury, S. Hota, S. Lakshmi Total Routhian Surface calculations have been performed with the Ultimate Cranker program (modified harmonic oscillator potential) as a function of epsilon2, epsilon4 and gamma deformation parameters on actinide nuclei with 94$\le $Z$\le $98 and 150$\le $N$\le $152. The equilibrium deformation trend is investigated with increasing frequencies. Nucleon alignments as a function of rotational frequency deduced from the calculations are compared with previous results reported in literature, both experimental as well as theoretical (Woods-Saxon potential). Results from the calculations will be presented and discussed in the context of new spectroscopic information in this region. [Preview Abstract] |
Friday, October 28, 2011 11:42AM - 11:54AM |
HE.00007: Spectroscopy of $^{244,245,246}$Pu S. Hota, P. Chowdhury, S. Lakshmi, S.K. Tandel, T. Harrington, E.G. Jackson, K. Moran, U. Shirwadkar, I. Ahmad, M.P. Carpenter, C.J. Chiara, J. Greene, C.R. Hoffman, R.V.F. Janssens, T.L. Khoo, F.G. Kondev, T. Lauritsen, C.J. Lister, E.A. McCutchan, D. Seweryniak, I. Stefanescu, S. Zhu In continuation of high-spin studies in the A$\sim $250 region via inelastic and transfer reactions, new spectroscopic measurements have been performed in the neutron rich $^{244,245,246}$Pu. High-spin states in these N=150,151,152 nuclei were populated using a $^{208}$Pb beam incident on a $^{244}$Pu target, with gamma rays detected by the Gammasphere array. In $^{244}$Pu, two new bands are observed which follow vibrational characteristics. In $^{245}$Pu, new rotational bands are observed through coincidences with the binary reaction partner $^{207}$Pb as well as transitions identified in light-ion transfer reactions. The ground state band in $^{246}$Pu is extended to J$^{\pi }$ = 20$^{+}$. The new results will be discussed in the context of emerging systematics of high-spin spectroscopic data in the Z$<$100 Cm$_{96}$[1] and Cf$_{98}$[2] isotones. 1. U. Shirwadkar, Ph.D. Thesis, U. Massachusetts Lowell, 2009. 2. S. K. Tandel et. al., Phys. Rev. C 82, 041301(R) (2010). [Preview Abstract] |
Friday, October 28, 2011 11:54AM - 12:06PM |
HE.00008: New level schemes and excitation modes of $^{117,118,119,120,122}$Cd Y.X. Luo, J.O. Rasmussen, C.S. Nelson, J.H. Hamilton, A.V. Ramayya, S.H. Liu, N.T. Brewer, J.K. Hwang, C. Goodin, S.J. Zhu, G.M. Ter-Akopian, A.V. Daniel, I.Y. Lee Analysis of high statistics triple coincidence fission $\gamma $ data from $^{252}$Cf at Gammasphere including angular correlations yielded well-expanded high-spin level schemes with more complete and reliable spin/parity assignments for $^{117-120,122}$Cd. Both the quasi-particle/hole couplings and quasi-rotational degrees of freedom are implied to play roles in these Cd isotopes. Evidence for triaxial shapes and octupole components in the Cd isotopes is presented. TRS calculations show an evolution from prolate shapes for mass number 115-118 to triaxial for 119-122. The model-independent spin $\sim $ h$\omega $ plots of the yrast bands indicate the role of quasi-rotational alignment of the (\textit{$\upsilon$}$h_{11/2})^{2}$ neutron pair and the blocking effect of the odd $h_{11/2}$ neutron. [Preview Abstract] |
Friday, October 28, 2011 12:06PM - 12:18PM |
HE.00009: Nuclear Structure in Neutron Rich Gd Nathan Brewer, J.C. Batchelder, J.H. Hamilton, A.V. Ramayya, C.J. Gross, K.P. Rykaczewski, R. Grzywacz, M. Madurga, D. Miller, D. Stracener, C. Jost, E. Zganjar, J.A. Winger, M. Karny, S.V. Paulauskas, S.H. Liu, M. Wolinska-Cichocka, S. Padgett, T. Mendez, K. Miernik, A. Kuzniak Deformed nuclei at midpoints between closed spherical shells form some of the best nuclear rotors known. Only a few nucleons away from the exact midshell in Z=66 and N=104, these nuclei have been shown to have very consistent I(I+1) spacing in the yrast band. By studying the energy systematics of the non-yrast and parent ground states we can further probe the structure of these nuclei. Nuclei for this study were produced via proton induced fission of $^{238}$U at HRIBF at ORNL. They were measured at the Low-energy RIB Spectroscopy Station (LeRIBSS) which utilizes beta and gamma detection as well as a MTC (Moving Tape Collector) which allows for parent lifetime measurements. In addition to 5 new levels in $^{162}$Gd,levels in $^{162,164}$Gd are both populated via beta- decay up to the 8$^{+}$ yrast levels. We will present and discuss new results from the beta decay of these isotopes. [Preview Abstract] |
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