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 JE: Nuclear Structure III (A=53-90) |
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Chair: Christopher Morse, University of Massachusetts Lowell Room: Junior Ballroom D |
Saturday, October 15, 2016 10:30AM - 10:42AM |
JE.00001: Charge radii of neutron-deficient $^{52, 53}$Fe K. Minamisono, B. A. Brown, A. J. Miller, D. M. Rossi, B. Maa$\ss$, W. N$\ddot{\rm o}$rtersh$\ddot{\rm a}$user, D. Garand, C. Sumithrarachchi, P. F. Mantica, R. Beerwerth, S. Fritzsche, A. Klose, Y. Liu, P. Müller, M. R. Pearson Shell closures can be identified as “kinks” in the chain of charge radii, $\left< r^2\right>$, which can be seen for the $N$ = 28 neutron shell closure up to $_{25}$Mn. The $\left< r^2\right>$ trends in the vicinity of $^{56}$Ni is of particular interest, since the $^{56}$Ni nucleus is known to be soft. The $\left< r^2\right>$ of neutron-deficient $^{52, 53}$Fe were determined in the present study using the bunched beam collinear laser spectroscopy at BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/MSU. The presence of a kink in the chain of $\left< r^2\right>$ at $N$ = 28 for the Fe isotopes was confirmed. The global behavior of the $\left< r^2\right>$ of Fe, and Ca thorough Ni isotopes, will be discussed. [Preview Abstract] |
Saturday, October 15, 2016 10:42AM - 10:54AM |
JE.00002: Quadrupole Moments of odd-A $^{53-63}$Mn: First use of optical pumping in the ISOLDE cooler/buncher Carla Babcock The technique of optical pumping has been used in the ISOLDE (CERN) cooler/buncher ion trap in order to study the previously inaccessible quadrupole moments of neutron-rich manganese ions via collinear laser spectroscopy. Previously, the insensitivity of the ground state atomic transitions to the quadrupole interaction prevented the determination of the electric quadrupole moment with any reasonable accuracy. Instead, a transition from an ionic metastable state was used and this state was populated via optical pumping. This was done in the bunching region of the ion trap, to allow multiple laser-ion interactions. Spectroscopic quadrupole moments were measured for the odd-even isotopes in the range $^{53-63}$Mn. They were compared to the predictions of three modern shell model effective interactions. The inclusion of both the $1 \nu g_{9/2}$ and $2 \nu d_{5/2}$ orbitals in the model space was thus shown to be necessary to reproduce the observed increase in the quadrupole deformation from $N=36$ onwards. Specifically, the inclusion of the $2\nu d_{5/2}$ orbital induces an increase in neutron and proton excitations across the proposed gaps at $N=40$ and $Z=28$, leading to an increase in deformation in the more neutron-rich isotopes. [Preview Abstract] |
Saturday, October 15, 2016 10:54AM - 11:06AM |
JE.00003: Electric Monopole Transition Strengths in Stable Nickel Isotopes Lee Evitts, Adam Garnsworthy, Tibor Kibedi Electric monopole ($E0$) transition strengths are a sensitive probe for investigating nuclear structure and shape coexistence. There is a need for $E0$ transition strengths in closed shell nuclei in order to develop our understanding of the mechanisms responsible for the generation of electric monopole strength. Simultaneous detections of $\gamma$ rays and internal conversion electrons must be measured in order to determine an $E0$ transition strength. A series of measurements in the stable nickel isotopes were performed at the Australian National University. Excited states in $^{58,60,62}$Ni were populated via inelastic proton scattering. The CAESAR array of Compton-suppressed HPGe detectors was used to measure the ($E2/M1$) mixing ratio of transitions from angular distributions of $\gamma$ rays. The Super-e spectrometer was used to measure electron-gamma branching ratios in order to extract $E0$ transition strengths for a number of $J^\pi \rightarrow J^\pi$ transitions. An overview of the experiments will be presented, along with preliminary results for $E0$ transition strengths between $J^{\pi} \neq 0$ states in the semi-magic nuclei, $^{58, 60, 62}$Ni. A comparison with the matrix elements obtained from a new microscopic model for $E0$ transitions will be made. [Preview Abstract] |
Saturday, October 15, 2016 11:06AM - 11:18AM |
JE.00004: Precision Mass Measurements of Neutron-Rich Co Isotopes Beyond N=40 Christopher Izzo, Georg Bollen, Maxime Brodeur, Martin Eibach, Kerim Gulyuz, James Kelly, Matthew Redshaw, Ryan Ringle, Rachel Sandler, Stefan Schwarz, Chandana Sumithrarachchi, Adrian Valverde, Antonio Villari For many years, the region near Z=28, N=40 has been a subject of great interest for the nuclear structure community due to spectroscopic signatures in $^{68}$Ni suggesting a subshell closure at N=40. Mass surfaces and their derivatives provide a complementary approach to shell structure investigations via separation energies, and mass measurements can therefore play an important role in understanding shell structure in the region of $^{68}$Ni. Penning trap mass spectrometry has provided precise measurements for a number of nuclei in this region, however a complete picture of the mass surfaces has so far been limited by the large uncertainty remaining for nuclei with N$>$40 along the iron and cobalt chains. Here we shall present the first Penning trap measurements of $^{68,69}$Co, performed at the Low Energy Beam and Ion Trap facility at the National Superconducting Cyclotron Laboratory, and discuss the importance of these measurements for understanding the evolution of nuclear structure in the region of $^{68}$Ni. [Preview Abstract] |
Saturday, October 15, 2016 11:18AM - 11:30AM |
JE.00005: Shape changes in neutron rich $N =$\textit{ 43} isotones Jasmine Sethi, A. Forney, W. B. Walters, J. Harker, C. J. Chiara, I. Stefanescu, R. V. F. Janssens, S. Zhu, M. P. Carpenter \textit{et al.} Nuclei in the transitional region with \textit{28 \textless Z \textless 50} and \textit{40 \textless N \textless 50} are very sensitive to shape changes with addition of individual nucleons due to close-lying neutron orbitals in the \textit{fpg} model space. A systematic comparison of the structure of $N =$\textit{ 43} isotones, focussing on new results on $^{\mathrm{75}}$Ge and $^{\mathrm{73}}$Zn will be presented. Both nuclei were populated in deep inelastic scattering reactions, $^{\mathrm{76}}$Ge $+ \quad^{\mathrm{208}}$Pb and $^{\mathrm{76}}$Ge $+ \quad^{\mathrm{238}}$U, at \textasciitilde 25{\%} above the Coulomb barrier, using Gammasphere and ATLAS facility at ANL. A number of new transitions and levels have been identified in both nuclei. The experimental results and their comparison to the theoretical calculations will be presented. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics under Contract numbers DE-AC02-06CH11357 and DE- AC02-05CH11231 and under Grant numbers DE-FG02-94ER40834 and by the Polish Ministry of Science Grant numbers 1P03B05929 and NN202103333. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility [Preview Abstract] |
Saturday, October 15, 2016 11:30AM - 11:42AM |
JE.00006: Decay properties of neutron-rich 74Co and predictions for 78Co Shintaro Go, Robert Grzywacz, Mazzocchi Chiara, Sean Liddick, Mohammad Alshudifat, Jon Batchelder, Thomas Baumann, Tom Ginter, Carl Gross, Karolina Kolos, Agnieszka Korgul, Aleksandra Ciemny, Stanley Paulauskas, Christpher Prokop, Mustafa Rajabali, Krzysztof Rykaczewski, Steven Taylor, Yongchi Xiao Experimental studies of doubly magic 78Ni are needed to provide critical data to test the robustness of the nuclear shell structure and model r-process. One of the best ways to investigate the shell structure of 78Ni is the decay of 78Co. While presently it is not possible to produce 78Co with sufficient rates, the decay measurements will be an essential study with new facilities and beam intensity upgrades. We measured the beta-decay properties of 74Co using fragmentation reaction at NSCL. Combining this result and other existing data around 78Ni enabled us to make predictions for the decay properties of 78Co. The half-life and beta-delayed neutron emission probability predicted by shell-model calculations will be presented for the chain of odd-odd cobalt isotopes. [Preview Abstract] |
Saturday, October 15, 2016 11:42AM - 11:54AM |
JE.00007: Study of $^{68}$Co low-energy structure via $\beta$ decay B.P. Crider, C.J. Prokop, S.N. Liddick, J. Chen, A.C. Dombos, N.R. Larson, R. Lewis, S.J. Quinn, A. Spyrou, A.D. Ayangeakaa, M.P. Carpenter, H.M. David, R.V.F. Janssens, T. Lauritsen, D. Seweryniak, S. Zhu, M. Al-Shudifat, S. Go, R. Grzywacz, J. Harker, W.B. Walters, J.J. Carroll, C.J. Chiara, F. Recchia, S. Suchyta The fragility of the $N=40$ subshell closure in neutron-rich nuclei is highlighted by the sudden onset of collectivity as protons are removed from the $\pi f_{7/2}$ single-particle state and has been attributed to shape coexistence between spherical and prolate-deformed configurations. A recent study of $^{68}$Co at NSCL concluded that the lowest-energy populated state was attributed to a deformed configuration, further extending the presence of shape coexistence to this nucleus. This work reports on $^{68}$Co from a $\beta$-decay experiment at NSCL utilizing the $\beta$ decay from $^{68}$Fe to populate low-spin states of $^{68}$Co. Coupling large statistics and half-life measurement capabilities, an expanded description of $^{68}$Co will be presented. [Preview Abstract] |
Saturday, October 15, 2016 11:54AM - 12:06PM |
JE.00008: Gamma-Gamma Angular Correlation Measurements With GRIFFIN Andrew MacLean The goal of this work was to explore the sensitivity of the Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei (GRIFFIN) 16 clover-detector $\gamma$-ray spectrometer at TRIUMF-ISAC to such $\gamma-\gamma$ angular correlations. The methodology was established using both experimental measurements and Geant4 simulations that were used to create angular correlation templates for the GRIFFIN geometry. Direct comparisons were made between experimental data sets and the simulated angular correlation templates. A first in-beam test of the $\gamma-\gamma$ angular correlation measurements with GRIFFIN was performed with a radioactive beam of $^{66}$Ga. Mixing ratios of $\delta = -2.1(2)$ and $\delta = -0.08(3)$ were measured for the $2^{+}\rightarrow 2^{+}\rightarrow 0^{+}$ 833-1039 keV and $1^{+}\rightarrow 2^{+}\rightarrow 0^{+}$ 2752-1039 keV cascades in the daughter nucleus $^{66}$Zn. These results are in good agreement with pervious literature values and the mixing ratio for the 833-1039 keV cascade has a higher precision. Also, the sensitivity to the 1333-1039 keV cascade, with its pronounced $0^{+}\rightarrow 2^{+}\rightarrow 0^{+}$ angular correlation, was measured.A test measurement of the superallowed Fermi $\beta$ emitter $^{62}$Ga will also be discussed. [Preview Abstract] |
Saturday, October 15, 2016 12:06PM - 12:18PM |
JE.00009: Spectroscopic factors near the r-process path using ($d,p)$ measurements at two energies D. Walter, J.A. Cizewski, T. Baugher, A. Ratkiewicz, B. Manning, S.D. Pain, F.M. Nunes, S. Ahn, G. Cerizza, C. Thornsberry, K.L. Jones To determine spectroscopic factors, it is necessary to use a nuclear reaction model that is dependent on the bound-state potential. A poorly constrained potential can drastically increase uncertainties in extracted spectroscopic factors. Mukhamedzhanov and Nunes [1] have proposed a technique to mitigate this uncertainty by combining transfer reaction measurements at two energies. At peripheral reaction energies (\textasciitilde 5 MeV/u), the external contribution of the wave function can be reliably extracted, and then combined with the higher energy reaction (\textasciitilde 40 MeV/u) with a larger contribution from the interior. The two measurements will constrain the single-particle asymptotic normalization coefficient, ANC, and enable spectroscopic factors to be determined with uncertainties dominated by the cross section measurements rather than in the bound-state potential. Published measurements of $^{\mathrm{86}}$Kr($d,p)$ at 5.5 MeV/u [2] have been combined with recent results at 35 MeV/u at the NSCL using the ORRUBA and SIDAR arrays of silicon-strip detectors. Preliminary analysis shows that the single-particle ANC can be constrained. The details of the analysis and prospects for measurements with rare isotope beams will be presented. This research by the ORRUBA Collaboration is supported in part by the NSF and the U.S. DOE. [1] A.M. Mukhamedzhanov and F.M. Nunes, Phys. Rev. C 72, 017602 (2005) [2] K. Haravu et al., Phys. Rev C 1,938 (1970) [Preview Abstract] |
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