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 KE: Nuclear Structure IV (A=91-132) |
Hide Abstracts |
Chair: Jasmine Sethi, University of Maryland Room: Junior Ballroom D |
Saturday, October 15, 2016 2:00PM - 2:12PM |
KE.00001: Gamma-ray spectroscopy of 131Sn81 via the (9Be,8Be $\gamma )$ reaction Sean Burcher, A. Bey, K. Jones, S.H. Ahn, A. Ayres, K.T. Schmitt, J. Allmond, A. Galindo-Urribari, D.C. Radford, J.F. Liang, C.D. Neseraja, S.D. Pain, S.T. Pittman, M.S. Smith, D.W. Stracener, R.L. Varner, D.W. Bardayan, P.D. O'Malley, J.A. Cizewski, M.E. Howard, B.M. Manning, R.F. Garcia Ruiz, R.L. Kozub, M. Matos, E. Padilla-Rodal Nuclear data in the region of the doubly-magic nucleus $^{\mathrm{132}}$Sn$_{\mathrm{82}}$ is useful for benchmarking nuclear structure theories due to the clean single-particle nature of the nuclear wavefunction near the closed shells. At the Holifield Radioactive Ion Beam Facility (HRIBF) neutron-rich beams in the $^{\mathrm{132}}$Sn$_{\mathrm{82}}$ region were produced via proton-induced fission of a Uranium-Carbide target. The CLARION array of HPGe detectors was coupled with the HyBall array of CsI detectors to allow for particle-gamma coincidence measurements. The gamma-ray de-excitation of the four lowest lying single-neutron states has been observed for the first time via the ($^{\mathrm{9}}$Be,$^{\mathrm{8}}$Be $\gamma )$ reaction. The excitation energy of these states have been measured to higher precision than was possible with the previous charged particle measurement. [Preview Abstract] |
Saturday, October 15, 2016 2:12PM - 2:24PM |
KE.00002: $^{124}$In Levels Populated in the $\beta$-decay of $^{124}$Cd J. C. Batchelder, N. T. Brewer, C. J. Gross, R. Grzywacz, J. H. Hamilton, M. Karny, A. Fijalkowska, S. H. Liu, K. Miernik, S. W. Padgett, S. V. Paulauskas, K. P. Rykaczewski, A. V. Ramayya, D. W. Stracener, M. Woli\'nska-Cichocka The $\beta$-decay of $^{124}$Cd into levels in $^{124}$In was reinvestigated at the Holifield Radioactive Ion Beam Facility (HRIBF). Fifty MeV protons were bombarded on aranium targets and the induced fission products were mass separated and deposited on a moving tape in the center of an array of $\gamma$-detectors. The resulting $\gamma$-$\gamma$ coincidences revealed appreciable disagreement with previous work and has resulted in a revised ordering of the low energy states in $^{124}$In. The resulting partial decay scheme has four energy levels, three of which are new. [Preview Abstract] |
Saturday, October 15, 2016 2:24PM - 2:36PM |
KE.00003: Mixing Ratios of Transitions in $^{\mathrm{116}}$Sn David Cross, J. Pore, C. Andreoiu, A. S. Chester, P. Voss, V. Bildstein, G. A. Demand, A. Diaz Varela, R. Dunlop, P. E. Garrett, B. Hadinia, B. Jigmeddorj, A. Laffoley, A. Liblong, C. Svensson, G. C. Ball, P. C. Bender, A. Garnsworthy, G. Hackman, D. Miller, B. Noakes, Z-M. Wang, R. Kanungo, J. L. Wood, S. W. Yates The $\beta $ decay of $^{\mathrm{116m1,g}}$In to $^{\mathrm{116}}$Sn, observed at TRIUMF-ISAC utilizing the 8$\pi $ array of 20 HPGe detectors augmented with 5 Si(Li) detectors, produced a high statistics data set from which E2/M1 mixing ratios from $\gamma \gamma $ angular correlations were obtained. Several new mixing ratios of transitions among the I$^{\mathrm{\pi }} \quad =$ 4$^{\mathrm{+}}$ states were measured for the first time. In addition, the E0 component of the 4$_{\mathrm{2}}^{\mathrm{+}} \quad \to $ 4$_{\mathrm{1}}^{\mathrm{+}}$ transition was determined. Previous analyses of $^{\mathrm{116}}$Sn have explained the nature and mixing of the 4$^{\mathrm{+}}$ states on the basis of shared phonon strength [1,2]. The results presented here indicate that models of $^{\mathrm{116}}$Sn should explore alternative interpretations of their character. This observation has implications for ongoing theoretical and experimental research on $^{\mathrm{116}}$Sn and neighboring tin isotopes. [1] H. Wienke \textit{et al}., Nucl. Phys. A 405, 237 (1983) [2] S. Raman \textit{et al.}, Phys. Rev. C 43, 521 (1991) [Preview Abstract] |
Saturday, October 15, 2016 2:36PM - 2:48PM |
KE.00004: Beta-delayed neutron emission studies with a C$^{7}$LYC array at CARIBU Gemma Wilson, Partha Chowdhury, Christopher Lister, Tristan Brown, Michael Carpenter, Thomas Chillery, Patrick Copp, Emery Doucet, Alan Mitchell, Guy Savard, Shaofei Zhu This work is a study of $\beta$-delayed neutron and $\gamma$ emission from $^{94}$Rb at CARIBU. Beta-delayed neutron emission studies are important in the astrophysical r-process, nuclear structure and for nuclear reactor safety and design. Approximately 150 $\gamma$ rays are known in the daughter $^{94}$Sr, many of which are unplaced. An estimated $26\%$ of $\gamma$ rays are thought to be missing. The probability of $\beta$-delayed neutron emission in $^{94}$Sr is $10.2(2)\%$. Recently[1], substantial $\gamma$-decay from above the neutron separation energy in $^{94}$Rb has been reported. This research is aimed at understanding this high-lying $\gamma$-strength. The experiment employed the X-Array (a high efficiency HPGe clover array), SCANS (Small CLYC Array for Neutron Scattering) and the SATURN decay station (Scintillator And Tape Using Radioactive Nuclei) for $\gamma$, fast neutron and $\beta$-particle detection, respectively. Data were collected in a triggerless digital data acquisition system, with detected $\beta,n,$ and $\gamma$ events correlated offline. Techniques, analysis and first results will be discussed. [1] J. L. Tain et al, Phys. Rev. Lett 115 (062502) 2015 [Preview Abstract] |
Saturday, October 15, 2016 2:48PM - 3:00PM |
KE.00005: $\beta$-delayed neutron spectroscopy around N=82 with VANDLE Miguel Madurga Flores, Andrea Gottardo, Robert Grzywacz The properties of nuclei close to magic numbers have become a reference for our understanding of nuclear structure. The $\beta$-decay of these nuclei offers a clean window to study both the properties of the parent and the daughter. Of course, a sizable fraction of the beta-decay of neutron rich-nuclei will populate neutron-unbound states in the daughter.\\ The Versatile Array of Neutron Detectors at Low Energy was developed at Oak Ridge National Laboratory for neutron spectroscopy following $\beta$-decay and nuclear reactions [1,2]. It consists in 50+ individual detector modules made of plastic scintillator to measure neutron energies using the time-of-flight technique.\\ Results from a recent campaign at ISOLDE, CERN, on the decay of $r$-process waiting points $^{130,132}$Cd will be presented.\\ \noindent{[1] S.V. Paulauskas et al. Nucl. Instr. and Methods A737, 22(2014).}\\ \noindent{[2] W.A. Peters et al., submitted.} \\ [Preview Abstract] |
Saturday, October 15, 2016 3:00PM - 3:12PM |
KE.00006: High-Statistics $\bf{\beta^+/EC}$-Decay Study of $^{122}$Xe Badamsambuu Jigmeddorj The Xe isotopes are centrally located in the $Z>50$, $N<82$ region that displays an extraordinarily smooth evolution of simple collective signatures. However, the collectivity of excited states in this region is very poorly characterized. There are spectroscopic hints to unusual structures in this region. The $0^+_3$ states in $^{124-132}$Xe are very strongly populated in $(^3He,n)$ reactions, suggesting a pairing vibrational structure influenced by proton subshell gaps, perhaps leading to shape-coexistence that could give rise to strong $E0$ transitions. Recent work on $^{124}$Xe has established nearly identical quadrupole collectivity for the pairing vibrational $0^+_3$ band and the ground state band. However, in $^{122}$Xe, the $0^+_3$ state has not been firmly identified. A high-statistics $^{122}$Cs $\beta^+/EC$ decay experiment to obtain detailed spectroscopic data for low-spin states was performed at the TRIUMF-ISAC facility using the 8$\pi$ $\gamma$-ray spectrometer and its auxiliary detectors including PACES, an array of five Si(Li) detectors, for conversion electron spectroscopy. The decay scheme has been considerably extended through a $\gamma$-$\gamma$ coincidence analysis, and $0^+$ states have been identified via $\gamma$-$\gamma$ angular correlations. [Preview Abstract] |
Saturday, October 15, 2016 3:12PM - 3:24PM |
KE.00007: Decay spectroscopy of $N < Z$ nuclei around $^{100}$Sn Joochun (Jason) Park Many interesting topics in both nuclear structure and nuclear astrophysics converge on the doubly-magic nucleus $^{100}$Sn and nuclei in its vicinity. Among them are the boundaries of proton dripline, the effect of $pn$ interaction in self-conjugate nuclei, and the decay properties required for $rp$-process calculations in nucleosynthesis models. Despite many studies, experimental knowledge of these nuclides has remained scarce due to low production cross sections and a lack of intense beams. However, record quantities of exotic $N \simeq Z$ isotopes around $^{100}$Sn were produced at RIKEN Radioactive Isotope Beam Factory, via fragmentation of a $^{124}$Xe beam on a thin $^{9}$Be target. Based on the obtained data, $^{89}$Rh and $^{93}$Ag have been confirmed to be proton unbound [1]. Half-lives of isotopes near the proton dripline will be presented with improved precision compared to literature values. In addition, strategies to determine $Q_\beta$ for $ft$ values, and consequently the Fermi/Gamow-Teller transition strengths of these isotope decays will be discussed. [1] I. Celikovic et al., Phys. Rev. Lett. 116, 162501(2016). [Preview Abstract] |
Saturday, October 15, 2016 3:24PM - 3:36PM |
KE.00008: ABSTRACT WITHDRAWN |
Saturday, October 15, 2016 3:36PM - 3:48PM |
KE.00009: Single particle structure and shapes of exotic Sr isotopes Steffen Cruz States within a nucleus that have different shapes that are close in energy are referred to as shape coexisting. A dramatic occurrence of shape coexisting states is observed in nuclei in the vicinity of Z=40, N=60, which is the subject of substantial current experimental and theoretical effort. An important aspect in this context is the evolution of single particle structure for N $<$ 60 leading up to the shape transition region, which can be calculated with modern large scale shell model calculations using a $^{78}$Ni core or Beyond Mean Field Models. One-neutron transfer reactions are a proven tool to study single-particle energies as well as occupation numbers. Here we report on the study of the single-particle structure in $^{96}$Sr via (d,p) one-neutron transfer reaction in inverse kinematics. The experiment presented was performed in the ISAC facility using the TIGRESS gamma-ray spectrometer in conjunction with the SHARC charged-particle detector. A thorough analysis of single particle states will improve our understanding of the onset of these unique structures, encouraging the ongoing theoretical discussions. Results discussed in the context of the evolution of single-particle structure will be presented. [Preview Abstract] |
Saturday, October 15, 2016 3:48PM - 4:00PM |
KE.00010: Doppler-shift lifetime measurements in $^{94}$Sr using the TIGRESS Integrated Plunger Aaron Chester Neutron-rich Sr isotopes are characterized by a sudden onset of quadrupole deformation at neutron number $N=60$ demonstrated by a dramatic drop in excitation energy of the first $2^+_1$ state. Though the emphasis is usually put on the sudden onset of collectivity at $N=60$, it is equally surprising that there is no onset of collectivity when adding up to 8 neutrons beyond the $N=50$ shell closure, as indicated by a previous measurement of low $B(E2)$ values of $\approx 10$~W.u.~in even-even Sr isotopes from $^{90}$Sr to $^{96}$Sr [1]. A high precision Doppler shift lifetime measurement of the first excited state in $^{94}$Sr using the TIGRESS Integrated Plunger (TIP) [2] can help elucidate whether the onset of collectivity is as sudden as generally assumed. An experiment aimed towards a high-precision ($<10$\%) measurement of the $B(E2,2^+_1\rightarrow 0^+_1)$ reduced transition probability in $^{94}$Sr was performed in December 2015 using inelastic scattering near the Coulomb barrier coupled with an recoil distance method lifetime measurement of a radioactive $^{94}$Sr beam. The device, experimental approach, analysis, and preliminary results will be presented and discussed. [1] Mach et al., Nucl. Phys. A 523 (1991) 197; [2] Voss et al., Nucl. Inst. and Meth. A 746 (2014) [Preview Abstract] |
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