Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session J3: Nuclear Structure II |
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Sponsoring Units: DNP Chair: Christopher Chiara, Army Research Laboratory Room: Holiday 2 |
Sunday, April 12, 2015 10:45AM - 10:57AM |
J3.00001: The 3$_{1}^{-}$ level in $^{56}$Fe N. Fotiades, M. Devlin, R.O. Nelson The question whether the 3076.2-keV, (3$^{-}$), or the 4509.6~keV, 3$^{-}$, is the first 3$^{-}$ level in $^{56}$Fe is important for reaction model calculations [see M. B. Chadwick {\it et al.}, Nucl. Data Sheets {\bf 118}, 1 (2014)]. The inclusion in the databases of the 3076.2-keV level will be discussed. A work by A. M. Demidov {\it et al.} [Phys. Atom. Nucl. {\bf 67}, 1884 (2004)] using the $^{56}$Fe(n,n$^{\prime}{\gamma}$) reaction and fast neutrons from a reactor, reported that the 3076.2-keV state does not exist and triggered the present work, where $\gamma$-$\gamma$ coincidence data in $^{56}$Fe, which are more definitive, were recorded with the GEANIE spectrometer comprised of 26 high-purity Ge detectors. The pulsed beam of the Los Alamos Neutron Science Center's WNR facility provided fast neutrons impinging on a $^{56}$Fe target. As we reported in Phys. Rev. C {\bf 81}, 037304 (2010), our experiment supported the assignment of the 4509.6~keV level as the first 3$^{-}$ state, with no observation in the gated spectra of the two transitions that were reported to decay out of the 3076.2-keV level by Z. Guo {\it et al.} [Nucl. Phys. {\bf A540}, 117 (1992)]. A plan to repeat the (p,$\gamma$) reaction that reported the observation of these two transitions will be discussed. [Preview Abstract] |
Sunday, April 12, 2015 10:57AM - 11:09AM |
J3.00002: Identification of deformed intruder states in semi-magic $^{70}$Ni C.J. Chiara, W.B. Walters, R.V.F. Janssens, D. Weisshaar and the U. of Maryland -- ANL -- MSU -- U. of Tokyo -- U. of Padua -- LBNL -- U. of Edinburgh -- U. of Aizu -- Orsay -- JAEA -- Central Michigan U. collaboration --- The structure of semi-magic $_{28}^{70}$Ni$_{42}^{{}}$ was investigated following complementary multinucleon-transfer and secondary fragmentation reactions. Changes to the higher-spin, presumed negative-parity states based on observed $\gamma$-ray coincidence relationships improve the agreement with shell-model calculations using effective interactions in the neutron $f_{5/2}pg_{9/2}$ model space. The second 2$^{+}$ and (4$^{+}$) states, however, can only be successfully described when proton excitations across the $Z=28$ shell gap are included. Monte-Carlo shell-model calculations suggest that the latter two states are part of a prolate-deformed intruder sequence, establishing an instance of shape coexistence at excitation energies lower than those observed recently in neighboring $^{68}$Ni. [Preview Abstract] |
Sunday, April 12, 2015 11:09AM - 11:21AM |
J3.00003: Zn-71 levels populated in neutron-capture-gamma reactions Andrew Huchison, Jessica Harker, William B. Walters, Mark Waite, Rick Paul The level structure of $^{71}$Zn was studied via the capture-gamma reaction on a highly-enriched $^{70}$Zn target at the NIST Center for Neutron Research NG-7 beam line. The neutron separation energy was determined to be 5832.5(5) keV. Low-spin levels populated in this reaction will be presented, compared with data from other measurements, and discussed. [Preview Abstract] |
Sunday, April 12, 2015 11:21AM - 11:33AM |
J3.00004: An Exploration of Structures in the Transitional Odd-Odd Nucleus $^{160}\textrm{Lu}$ S.T. Hallgren, D.J. Hartley, M.A. Riley, J. Baron, S. Miller, J. Simpson, P.J.R. Mason, E.S. Paul, A.J. Boston, H.C. Boston, P.J. Nolan, J. Wright, R.V.F. Janssens, A.D. Ayangeakaa, M.P. Carpenter, F.G. Kondev, T. Lauritsen, S. Zhu, L.L. Riedinger, J. Carroll, C.J. Chiara, J. Harker, U. Garg, J. Matta, W.C. Ma It is known that a transition between spherical and deformed isotopes of lutetium occurs near $N=88$. The odd-odd nucleus $^{160}\textrm{Lu}$ ($N=89$) was selected for a study of structural characteristics in this transitional region. High-spin states of $^{160}\textrm{Lu}$ were populated using the $^{120}\textrm{Sn}(^{45}\textrm{Sc},5\textrm{n})^{160}\textrm{Lu}$ reaction and gamma-ray transitions were studied using the Gammasphere spectrometer. Known structures were extended to much higher spin and a new sequence was identified. The resulting bands and nuclear configurations were studied and compared with neighboring isotopes of lutetium. [Preview Abstract] |
Sunday, April 12, 2015 11:33AM - 11:45AM |
J3.00005: Investigation of a Peak-Like Feature Observed in the Triton Energy Spectra from the $^{152,154}$Sm(p,t) Reactions P. Humby, E. Wilson, C.W. Beausang, A. Simon, K. Gell, T. Tarlow, G. Vyas, T.J. Ross, R.O. Hughes, J.T. Burke, R.J. Casperson, J. Koglin, S. Ota, J.M. Allmond, M. McCleskey, E. McCleskey, A. Saastamoinen, R. Chyzh, M. Dag Isotopically enriched $^{152,154}$Sm targets were bombarded with 25 MeV protons from the K-150 cyclotron at the Cyclotron Institute of Texas A\&M University. The outgoing charged particles and $\gamma$ rays were detected using the STARLiTeR array, which consists of a highly segmented $\Delta$E-E silicon telescope and six BGO shielded HPGe clover detectors. A peak-like feature was observed in the triton energy spectra from the $^{152,154}$Sm(p,t) reactions at excitation energies of approximately 3 MeV for the $^{152}$Sm(p,t) reaction and 2.2 MeV for the $^{154}$Sm(p,t) reaction. Discrete states with cross sections as large as approximately 9\% of the ground state cross section were identified in this feature using particle-$\gamma$ and particle-$\gamma$-$\gamma$ coincidences. The range of spins populated appears to be unusually large. [Preview Abstract] |
Sunday, April 12, 2015 11:45AM - 11:57AM |
J3.00006: Using the 154Sm(p,d) reaction to extend the level scheme of 153Sm to the continuum region Emma Wilson, Cornelius Beausang, Peter Humby, Anna Simon, Timothy Ross, Richard Hughes, James Burke, Robert Casperson, Johnathon Koglin, Shuya Ota, James Allmond, Matthew McCleskey, Ellen McCleskey, Antti Saastamoinen, Roman Chyzh, Kristen Gell, Tom Tarlow, Gargi Vyas Following an experiment performed at the Cyclotron Institute of Texas A\&M University, the level scheme of $^{153}$Sm is in the process of being extended. A beam of protons accelerated to 25 MeV impinged on an isotopically enriched $^{154}$Sm target, inducing a (p,d) reaction, thereby producing energetically excited $^{153}$Sm reaction products. The resulting $\gamma$-rays and deuterons were detected by the STARLiTe array, which consists of six Compton-suppressed HPGe gamma-ray detectors, and a $\Delta$E-E Si telescope for charged particle identification. In the ongoing analysis of these data, the identification of new $\gamma$-rays has been possible. The deuteron spectrum will be used to identify high-lying continuum states, and angular momentum transfer values will be assigned using angular distributions and comparison with DWBA calculations. This work was partly supported by the US DofE under grant numbers DE-NA0001801, DE-FG02-05ER41379(UofR); DE-AC52-07NTJKTG(LLNL). [Preview Abstract] |
Sunday, April 12, 2015 11:57AM - 12:09PM |
J3.00007: Search for High-Spin Triaxial Strongly Deformed Bands in $^{166}$W W.C. Ma, S. Mukhopadhyay, P. Premarashna, J.C. Marsh, R.B. Yadav, U. Garg, J.T. Matta, A.D. Ayangeakaa, Y. Gupta, R.V.F. Janssens, M.P. Carpenter, T. Lauritsen, S. Zhu, F.G. Kondev, J. Chen, D.J. Hartley, D.C. Biswas, R. Chakrabarti, C. Petrache, C.J. Chiara High-spin triaxial strongly deformed (TSD) structures, including families of wobbling bands, have been observed in several Lu and Ta Isotopes near $A \sim 165$, and in $^{164,168}$Hf as well.\footnote{J. C. Marsh {\it et al}., Phys. Rev. C {\bf 88}, 041306(R) (2013).} The nuclide $^{166}$W is close to the proton and neutron shell gaps at large triaxiality. Theoretical studies suggest that the elevated yrast line of $^{166}$W, an $N = 92$ isotone, may reduce the excitation energy of the predicted TSD structure relative to its normal deformed yrast line, resulting in an increased population of the TSD bands. A Gammasphere experiment has been performed at the ATLAS facility to search for such structures through the $^{110}$Pd($^{60}$Ni,4n) reaction. Previously known bands have been extended to higher spins, and several new bands have been identified. Further data analysis is in progress, results will be presented. [Preview Abstract] |
Sunday, April 12, 2015 12:09PM - 12:21PM |
J3.00008: Analysis of the Nuclear Structure of $^{186}$Re Using Neutron-Induced Reactions David Matters, John McClory, James Carroll, Chris Chiara, Nikolaos Fotiades, Matt Devlin, Ron O. Nelson Evaluated nuclear structure data for $^{186}$Re identifies the majority of spin-parity assignments as tentative, with approximate values associated with the energies of several levels and transitions. In particular, the absence of known transitions that feed the $J^{\pi}=8^{+}$ isomer motivates their discovery, which would have astrophysical implications and a potential application in the development of an isomer power source. Using the GErmanium Array for Neutron Induced Excitations (GEANIE) spectrometer at the Los Alamos Neutron Science Center (LANSCE) Weapons Neutron Research (WNR) facility, the (n,2n$\gamma$) and (n,n'$\gamma$) reactions in a 99.52\% enriched $^{187}$Re target were used to measure $\gamma$-ray excitation functions in $^{186}$Re and $^{187}$Re, respectively. A preliminary analysis of the data obtained from the experiment reveals several new transitions in $^{186}$Re and $^{187}$Re. [Preview Abstract] |
Sunday, April 12, 2015 12:21PM - 12:33PM |
J3.00009: Cross sections of intermediate energy abrasion-fission fragments from cobalt to silver Michael Bowry Cross sections of A$\approx $100 fission products have been measured across 21 isotopic chains from Z$=$27 (Co) to 47 (Ag) following in-flight fission of a uranium-238 beam at 80 MeV per nucleon. The uranium beam was fragmented upon an active diamond target located at the target positon of the S800 spectrograph and surrounded by the Gamma-Ray Energy Tracking Array (GRETINA). Fission products were identified on an event-by-event basis by correlating time-of-flight and energy-loss measurements in the S800 with in-flight gamma-decays reconstructed by GRETINA in the rest frame of the projectile (v/c $\approx $ 0.4). Transmission through the S800 was determined experimentally and from simulations performed using LISE$++$: the results of these techniques are compared. The cross sections shall form a valuable benchmark for the production of radioisotopes in phenomenological fission models at intermediate energies that rely on, for example, parameters extrapolated from high-energy fragmentation studies (\textgreater \textgreater 100 MeV per nucleon). Three quarters of a century after the first description of fission decay, fission continues to serve as an insightful probe for nuclear spectroscopy through a variety of direct and indirect experimental methods. [Preview Abstract] |
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