Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session PE: Nuclear Structure V (A>133) |
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Chair: Gemma Wilson, University of Massachusetts Lowell / Argonne National Laboratory Room: Junior Ballroom D |
Sunday, October 16, 2016 10:30AM - 10:42AM |
PE.00001: Reinvestigation of octupole correlations in $^{146,147}$La E.H. Wang, W. Lewis, C.J. Zachary, J.H. Hamilton, A.V. Ramayya, J.K. Hwang, S.H. Liu, N.T. Brewer, Y.X. Luo, J.O. Rasmussen, S.J. Zhu, G.M. Ter-Akopian, Yu.Ts. Oganessian High spin states of neutron rich $^{146,147}$La have been reinvestigated by $\gamma$-$\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$-$\gamma$ coincidence data from a $^{252}$Cf spontaneous fission experiment by using Gammasphere. Thirty-two new transitions and seventeen new levels in $^{146}$La are observed. Two new bands in $^{146}$La have been established. One of them is proposed to be the octupole parity partner of the previously known band. Twenty new transitions and thirteen new levels in $^{147}$La are observed. The ground state band of $^{147}$La has been established with a proposed 5/2$^+$ band-head. Angular correlations of cascades have been used to study the spins and parities of the states. The $B(E1)/B(E2)$ ratios between the proposed octupole bands in $^{146,147}$La have been measured showing decreasing octupole deformation from $^{144}$La to $^{146}$La, and from $^{145}$La to $^{147}$La. The backbending phenomenon of the four bands in $^{147}$La has been studied. [Preview Abstract] |
Sunday, October 16, 2016 10:42AM - 10:54AM |
PE.00002: Search for E0 Transitions in $^{154}$Gd S. Y. Strauss, A. Aprahamian, C. Casarella, P. Fasano, B. Frentz, G. Gilardy, T. Kuta, E. Lamere, J. Long, K. Manukyan, A. McCoy, S. Moylan, A. Nelson, C. Reingold, M. Skulski, M. K. Smith, W. Tan, B. Vande Kolk, C. Hughes, X. James, S. R. Lesher, M. Lowe, E. Temanson Recent studies have shown the existence of 16 0+ states in $^{154}$Gd. Understanding the nature of these low-lying 0+ states in deformed nuclei remains one of the open questions in nuclear structure. A recent review indicates that it is important to measure the E0s, B(E2) values, and transfer reaction cross sections to fully determine the nature of 0+ states. We will report on our search for E0 transitions between these states in $^{154}$Gd following the $^{152}$Sm($\alpha$,2n) reaction using the Internal Conversion Electron Ball (ICEBall) array in coincidence with $\gamma$-rays at the University of Notre Dame Nuclear Science Laboratory (NSL). ICEBall was re-implemented at the NSL 3 years ago and the $\gamma$-rays were detected by the HPGe detectors of Clovershare. Details of the experiment and preliminary results will be presented. [Preview Abstract] |
Sunday, October 16, 2016 10:54AM - 11:06AM |
PE.00003: $\beta$-decay of $^{134}$Sb as Calibration for $\beta$-Delayed Neutron Measurements Performed with Trapped Ions K. Siegl, A. Aprahamian, N.D. Scielzo, G. Savard, J.A. Clark, A.F. Levand, M. Burkey, S. Caldwell, A. Czeszumska, T.Y. Hirsh, K. Kolos, S.T. Marley, G.E. Morgan, E.B. Norman, A. Nystrom, R. Orford, S. Padgett, A. Pérez Galván, K.S. Sharma, S.Y. Strauss, B.S. Wang The decay of radioactive ions confined in an RF ion trap allows indirect measurements of beta-delayed neutron (BDN) emission, by measuring the momentum of the recoiling ion which can be much larger from neutron emission than from only lepton recoil. This method removes most of the systematic errors associated with neutron detection but introduces dependencies on specifics of the decay and interactions of the ion with the RF fields. In addition to BDN emission precursors, measurements were made of the $^{134}$Sb beta decay with this technique at Argonne National Laboratory using beams from the CARIBU facility. The $^{134}$Sb decay is a good calibrant for understanding the transit of the recoiling ions to the detectors because it has a simple decay scheme, with most of the decay intensity proceeding through a first-forbidden transition to the ground state of $^{134}$Te. These results will be discussed. [Preview Abstract] |
(Author Not Attending)
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PE.00004: Decay spectroscopy of neutron-rich $^{134}$Sb at the CARIBU facility Karolina Kolos, Nicholas Scielzo, Stephen Padgett, Elizabeth A. McCutchan, Alan John Mitchell, Christopher J. Lister, Patrick Copp, Jason A. Clark, Mike P. Carpenter, Guy Savard, Shaofei Zhu, Eric B. Norman, Ani Apbrahamian, Kevin Siegl, Elizabeth Heckmaier, Scott Marley Neutron-rich $^{134}$Sb is one of a few isotopes (together with $^{92}$Rb, $^{96}$Y and $^{142}$Cs) that have a large branching ratio to decay to the ground state via a $0^{-}\rightarrow 0^{+}$ first-forbidden transition. Previous measurements have indicated that 97.5\% of the decays of $^{134}$Sb ground state populate the ground state of $^{134}$Te directly. However, a recent experiment using an ion trap indicated that this number may be lower. In order to confirm the $\beta$-decay branching ratios, an experiment was carried out to measure the decay properties of $^{134}$Sb/$^{134m}$Sb using the X-Array (a highly efficient HPGe clover array) and SATURN (a plastic scintillators and tape-transport system) decay-spectroscopy station at the CARIBU radioactive ion-beam facility at Argonne National Laboratory. Results on the analysis will be presented. [Preview Abstract] |
Sunday, October 16, 2016 11:18AM - 11:30AM |
PE.00005: Decay spectroscopy of $^{257,258}$Db in the vicinity of the N=152 deformed shell gap Marija Vostinar Valuable information on the existence and the position of the island of superheavy stability can be obtained by studying the structure of elements in the transfermium region (Z>100). Of particular interest are the isotopes around the deformed shell gaps of N=152 and N=162, where some of the single particle states relevant for the opening of these gaps are also relevant for the spherical shell closure in the superheavy region at N= 172 or N=184. In our study we have investigated $^{257}$Db (N=152) and $^{258}$Db. We confirmed that $^{257}$Db has at least two states with different half-lives decaying by $\alpha$ particle emission into different states of $^{253}$Lr, which further decays by $\alpha$ emission with different half-lives. Indication of two states with different half-lives for $\alpha$ decay in $^{258}$Db was confirmed. Additional information on the $\gamma$-ray decay of excited levels in $^{250}$Md was gathered and a tentative level scheme was proposed. The electron capture branch of $^{258}$Db was measured directly, and the $\alpha$ decay of $^{258}$Rf was confirmed. Yet, the branching ratio is significantly lower compared to the previously published value. [Preview Abstract] |
Sunday, October 16, 2016 11:30AM - 11:42AM |
PE.00006: A Study on Low Spin States in $^{154}$Gd Using $(p,p^{\prime})$ Reaction Harris Bidaman, B. Hadinia, P. E. Garrett Located at the stability line, the low lying spin states of the $^{154}$Gd nucleus were investigated at the University of Jyv\"{a}skyl\"{a} accelerator laboratory in Finland using the $^{154}$Gd$(p,p^{\prime}{\gamma})$ reaction. A proton beam of 12 MeV was used to excite the $^{154}$Gd target, with the gamma-rays from the reaction detected with the JUROGAM II array, while the LISA charged-particle spectrometer was used for detection of the inelastically scattered protons. This experiment marked one of the first uses of the LISA spectrometer at Jyv\"{a}skyl\"{a}, which enabled the efficient tagging of the proton-emitting reactions, thus helping to distinguish between the $(p,p^{\prime})$ and the much more copious $(p,xn)$ channels. By analysing the peaks obtained from the gamma-gamma, and gamma-gamma-proton coincidence matrices, a decay scheme has been built using the RadWare software Escl8r. Experimental methods, new transitions, and future steps will be discussed. [Preview Abstract] |
Sunday, October 16, 2016 11:42AM - 11:54AM |
PE.00007: Investigating the nature of excited 0$^+$ states populated in the $^{162}Er$(p,t) reaction C. Burbadge, P.E. Garrett, V. Bildstein, A. Diaz Varela, M.R. Dunlop, R. Dunlop, D.S. Jamieson, D. Kisliuk, K.G. Leach, J. Loranger, A.D. MacLean, A.J. Radich, E.T. Rand, C.E. Svensson, G.C. Ball, S. Triambak, T. Faestermann, R. Hertenberger, H.-F. Wirth A continuing challenge in nuclear structure physics is the determination of the nature of low-lying excited 0$^+$ states. Various approaches have been implemented to interpret the occurence of these states, such as vibrational excitations in $\beta$ and $\gamma$ phonons or pairing excitations. One of the difficulties, however, in resolving the nature of these states is that there is a paucity of data, particularly for the excited $0^+$ states. Two-neutron transfer reactions are ideal for probing $0^{+}$$\rightarrow$ $0^{+}$ transitions in deformed nuclei. Excited $0^+$ states in $^{160}$Er have been studied via the ($p,t$) reaction at the Maier-Leibnitz Laboratory in Garching, Germany. Reaction products were momentum-analyzed with a Q3D magnetic spectrograph. The variance in the cross section of these low-lying excited $0^+$ states suggests a special character for the 0$^+_2$ state. Final results of the relative population of the excited 0$^+$ states will be presented. [Preview Abstract] |
Sunday, October 16, 2016 11:54AM - 12:06PM |
PE.00008: A transition centric approach to automatic level scheme determination Greg Demand, Paul Garrett, Jim Waddington Powerful $\gamma$-ray spectrometers are capable of rapidly collecting large data sets that incorporate hundreds of transitions. The determination of nuclear level schemes from the resulting experimental data is time consuming and is a substantial obstacle to the rapid development and formulation of new ideas, particularly when examining trends amongst large numbers of nuclei. This presentation will introduce a new transition-centric framework for level scheme determination. Using a transition-centric level scheme representation that closely matches the form of the experimental data allows for the derivation of an analytical formula that directly relates experimental data to level scheme structure. This approach transforms level scheme determination into a moderately complicated optimization problem. These developments, in combination with a simulated annealing optimization algorithm will be used to demonstrate the automatic determination of a level scheme derived from simulated $^{152}$Eu$^g$ $\beta^+$/EC decay data. [Preview Abstract] |
(Author Not Attending)
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PE.00009: Studies of the Hg isotopes via reactions Alejandra Diaz Varela, V. Bildstein, P.E. Garrett, A.T. Laffoley, A.D. MacLean, E.T. Rand, C.E. Svensson, G.C. Ball, T. Faestermann, R. Hertenberger, H.-F. Wirth The $^{199}$Hg isotope holds the most stringent upper limit for a nuclear electric dipole moment (EDM) to date. The experimental limit on the observed atomic EDM for $^{199}$Hg is converted to a limit on the nuclear EDM via a calculation of the Schiff moment, requiring knowledge of the nuclear structure of $^{199}$Hg. Ideal information to further contrain the $^{199}$Hg Schiff moment theoretical models would be the $E3$ and $E1$ strength distributions to the ground state, and $E2$ transitions amongst excited states. While the high level density of $^{199}$Hg makes those determinations challenging, complimentary information can be obtained from exploring surrounding even-even Hg isotopes.\\ As part of a campaign to study the Hg isotopes near $^{199}$Hg, two reactions, $^{198}$Hg$(d,d^{\prime})^{198}$Hg and $^{198}$Hg$(d,p)^{199}$Hg, were studied using the Q3D spectrograph at the Maier-Leibnitz Laboratory (MLL) in Garching, Germany. A 22 MeV deuterium beam was used to impinge a $^{198}$Hg$^{32}$S target. The $(d,d^{\prime})$ reaction allows us to probe the desired $E2$ and $E3$ matrix elements, while the \textit{(d,p)} reaction provides information on the neutron single-particle states of $^{199}$Hg. Work to date will be presented. [Preview Abstract] |
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