Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session NC: Nuclear Structure IV |
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Chair: Calem Hoffman, Argonne National Laboratory Room: Salon 3 |
Saturday, October 28, 2017 8:30AM - 8:42AM |
NC.00001: Symmetry restoration for mixed-spin pairing states in heavy nuclei Ermal Rrapaj, Alexandros Gezerlis, Augusto Macchiavelli Hatree-Fock Bogoliubov (HFB) mean field theory is the method of choice for describing heavy nuclei and has been very useful in nuclear physics over the decades. However, the wave-function obtained usually does not respect the symmetries of the Hamiltonian it is based upon. In this talk, I will focus on the ground state wave-function obtained by the gradient descent method and recent developments in projecting onto eigenstates of fixed particle number, isospin, and nuclear spin. The isotopes under investigation will be selected nuclei with A = 132, which exhibit spin-singlet, spin-triplet, and mixed-spin pairing. This work is meant to serve as a guide for future experimental searches of mixed-spin pairing in heavy nuclei. [Preview Abstract] |
Saturday, October 28, 2017 8:42AM - 8:54AM |
NC.00002: Concurrent Mass Measurement and Laser Spectroscopy for Unambiguous Isomeric State Assignment Daniel Lascar, Carla Babcock, Jack Henderson, Matt Pearson Recent work by the TITAN group at TRIUMF on isomeric state mass measurements of odd-A, neutron-rich cadmium nuclei has shown a disconnect between experiment and theory in $^{\mathrm{127g,m}}$Cd. The spin and parity assignments of the ground and isomeric states are assigned as 3/2$^{\mathrm{+}}$ and 11/2$^{\mathrm{-}}$, respectively, primarily via systematic arguments. Conversely, state of the art shell model and \textit{ab initio} calculations show a reversal of the states, predicting a ground state of 11/2$^{\mathrm{-}}$ and a 3/2$^{\mathrm{+}}$ isomer. Penning Trap Mass Spectrometry (PTMS) can measure the energy separation between the ground state and the isomer without ambiguity but cannot, on its own, comment on the spin and parity. Collinear Laser Spectroscopy (CLS) experiments have been performed on $^{\mathrm{127}}$Cd and have elegantly demonstrated the existence of both 3/2$^{\mathrm{+}}$ and 11/2$^{\mathrm{-}}$ states. What CLS cannot do, on its own, is assign an ordering to those states. If, however, a PTMS and CLS experiment could be performed concurrently using identical beams from the same facility then there exists sufficient information shared between both experiments that a definitive assignment can be made. We present a concept for a new slate of measurements using existing experimental facilities simultaneously, with shared resources, to definitively assign spin and parity for ground and isomeric states in short-lived nuclei. [Preview Abstract] |
Saturday, October 28, 2017 8:54AM - 9:06AM |
NC.00003: $\beta$-delayed spectroscopy of neutron-hole single particle states in $^{133}$Sn Miguel Madurga Flores, Robert Grzywacz, Rin Yokoyama, Thomas King, Maninder Singh The nuclear beta-decay offers a well understood and selective probe to study the structure of the daughter. Close to magic nuclei, this selectivity can be exploited to study the properties of states involving specific single-particle orbitals. Neutron single-hole states in $^{133}$Sn were studied for the first time in the beta-delayed neutron emission of $^{133}$In at the ISOLDE facility, CERN. Neutron energies and intensities were observed using the IDS Neutron Detector, a time-of-flight detector array consisting of 26 plastic scintillator bars [1]. Preliminary results will be discussed. \\ \\ ~[1] W.A. Peters et al., Nucl. Instr. and Meth. A836, 122 (2016). [Preview Abstract] |
Saturday, October 28, 2017 9:06AM - 9:18AM |
NC.00004: Studies of Exotic Nuclei using Coulomb Excitation at HRIBF Alfredo Galindo-Uribarri We describe highlights of single-step Coulomb-excitation experiments done at the Holifield Radioactive Ion Beam Facility (HRIBF) using pioneer techniques, methods and instrumentation developed specifically for this purpose during the last decade and a half. These experiments were aimed to the study of neutron-rich nuclei primarily at or near the magic numbers. HRIBF was the premier ISOL facility for the production of high quality and purity radioactive ion beams for 15 years until April 2012. We discuss topics such as the study of measurements of B(E2), Q values, and g factors of low-lying states along important isotopic and isotonic chains using new particle-gamma instrumentation and techniques. We give a brief description of future plans. [Preview Abstract] |
Saturday, October 28, 2017 9:18AM - 9:30AM |
NC.00005: Study of high-j neutron excitations outside $^{136}$Xe R. Talwar, B. P. Kay, A. J. Mitchell, S. Adachi, J. P. Entwisle, Y. Fujita, G. Gey, S. Noji, H. J. Ong, J. P. Schiffer, A. Tamii The character of single-neutron excitations outside of $N=82$ has been studied using nucleon transfer reactions in terms of the energy centroid of their strength as well as the fragmentation of this strength among the actual states of the nucleus. However, extending the systematic study of the $N=83$ isotones to $^{137}$Xe has been challenging due to xenon being a gas at room temperature. Though several attempts have been made, a quantitative determination of the spectroscopic factors for the neutron 9/2$^-$ and 13/2$^+$ excitations in $^{137}$Xe is still lacking. In the present work, we report on a study of the $^{136}$Xe($\alpha$,$^3$He)$^{137}$Xe reaction carried out at 100 MeV to probe the $\ell=5$, 9/2$^-$ and $\ell=6$, 13/2$^+$ single-neutron excitations. The experimental technique and results will be presented discussing them in context of the evolution of these single-neutron excitations and the influence of the tensor interaction on the neutron single-particle states as the proton orbits are filling. [Preview Abstract] |
Saturday, October 28, 2017 9:30AM - 9:42AM |
NC.00006: Level lifetimes and the nuclear structure of $^{134,136}$Xe from inelastic neutron scattering E.E. Peters, A. Chakraborty, B.P. Crider, T.J. Ross, S.F. Ashley, E. Elhami, A. Kumar, S.H. Liu, M.T. McEllistrem, S. Mukhopadhyay, J.N. Orce, F.M. Prados-Est\'{e}vez, S.W. Yates, S.F. Hicks The level structures of $^{134, 136}$Xe were studied with the inelastic neutron scattering reaction followed by $\gamma$-ray detection. Highly enriched solid XeF$_2$ samples were used in the measurements. A number of level lifetimes were determined for the first time with the Doppler-shift attenuation method, and the low-lying excited states were characterized from this new spectroscopic information. In $^{134}$Xe, the third excited state, a tentative $0^+$ level, was verified. The $3^-$ octupole phonon has been confirmed, and the complete negative-parity multiplet resulting from the $\nu (1h_{11/2}2d_{3/2})$ configuration has been tentatively identified for the first time in the $N = 80$ isotones. In $^{136}$Xe, a nucleus with a closed $N = 82$ neutron shell, several spins and parities of the states below 3 MeV in excitation energy have been firmly assigned for the first time, or have been re-assigned. New insights into the structures of these nuclei will be discussed. [Preview Abstract] |
Saturday, October 28, 2017 9:42AM - 9:54AM |
NC.00007: E0 components of J$^\pi\rightarrow$J$^\pi$ Transitions in $^{154}$Gd} Sabrina Strauss, Ani Aprahamian, Clark Casarella, Patrick J. Fasano, Bryce Frentz, Khachatur Manukyan, Craig Reingold, Mallory Smith, Wanpeng Tan, Shelly Lesher, Carter Hughes, Xavier James, Marcus Lowe, Eli Temanson E0 components of transitions between two states of the same spin and parity are challenging to measure, with sparse information available in nuclear databases. A recent study of $^{154}$Gd (D. A. Meyer et al, PRC 044309(2006)) showed the nucleus to have 16 0$^+$ states. $^{154}$Gd is well-studied by a number of reactions, hence it is an ideal candidate to search for E0 transitions. We will report on our results for transitions 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 4 years ago and the $\gamma$-rays were detected by Clovershare, segmented HPGe detectors purchased by the Yale Nuclear Structure Laboratory that are shared by a consortium of universities and laboratories for experimental campaigns. [Preview Abstract] |
Saturday, October 28, 2017 9:54AM - 10:06AM |
NC.00008: Identification of new transitions and levels in $^{163,165}$Gd and $^{163}$Tb from $\beta$ decay studies C.J. Zachary, N.T. Brewer, E.H. Wang, J.C. Batchelder, R. Grzywacz, C.J. Gross, K.P. Rykaczewski, J.H. Hamilton, A.V. Ramayya An investigation of $\gamma$-rays emitted following $^{163,165}$Eu $\beta$ decay to $^{163,165}$Gd and $^{163}$Gd $\beta$ decay to $^{163}$Tb has been performed. Data were collected at the LeRIBSS station of the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory with an array of four Clover HPGe detectors for $\gamma$-rays and 2 plastic scintillators for $\beta$ detection. The $\gamma$-rays were identified as belonging to $^{163}$Gd, $^{165}$Gd, and $^{163}$Tb via mass selection and $\gamma$-$\gamma$-$\beta$ or $\gamma$-$\gamma$ coincidence. In total 71 new $\gamma$-ray transitions were observed in $^{163}$Gd and 3 new $\gamma$-ray transitions from $^{165}$Gd have been identified for the first time. Among the new transitions in $^{163}$Gd the data show evidence for transitions of near 50 keV and high energy transitions of up to 2 MeV depopulating from the same energy level. This feature is atypical in previous nuclear structure studies and needs further experimental and theoretical consideration. Additionally the first observation of 11 $\gamma$-rays from $^{163}$Tb, between already known levels, has been made. [Preview Abstract] |
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