Bulletin of the American Physical Society
76th Annual Meeting of the Southeastern Section of APS
Volume 54, Number 16
Wednesday–Saturday, November 11–14, 2009; Atlanta, Georgia
Session HC: Nuclear Structure and Atomic Physics |
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Chair: Alfred Msezane, Clark Atlanta University Room: Paris |
Friday, November 13, 2009 10:45AM - 10:57AM |
HC.00001: Creating and trapping molecular negative ions in a Penning ion trap John N. Yukich, Andrew Muhich Numerous experiments have investigated the properties and dynamics of atomic negative ions. Similar experiments can be conducted with molecular negative ions. Laser photodetachment spectroscopy of such ions is more complicated due to rotational and vibrational structure, and often yields spectroscopic benchmarks such as rotational constants. We report on efforts to create and trap several molecular negative ions including S$_{2}^{-}$, OD$^{-}$, and SH$^{-}$ in a Penning ion trap. The ions are created in the trap by dissociative attachment to a carrier gas. Various techniques are used to confirm the identity of the trapped species, including ion cyclotron resonance methods. Future experiments will focus on laser photodetachment spectroscopy of these and other ions with an eye toward measurement of their molecular constants. [Preview Abstract] |
Friday, November 13, 2009 10:57AM - 11:09AM |
HC.00002: Determination of the $^1S_0$ Neutron-Neutron Scattering Length Using nd Breakup in Recoil Geometry at 19 MeV S. Tajima, A.S. Crowell, J. Deng, J. Esterline, C.R. Howell, M.R. Kiser, R.A. Macri, W. Tornow, B.J. Crowe III, R.S. Pedroni, W. Von Witsch, H. Wita{\L}a There is a significant discrepancy between the recent measurements of the $^1S_0$ neutron-neutron ({\it nn}) scattering length ($a_{nn}$). Gonz$\acute a$lez Trotter {\em et al.} [1] reported a value of $a_{nn} = -18.7 \pm 0.6$ fm from their nn coincidence cross-section measurements at a neutron beam energy of 13 MeV, while Huhn {\em et al.} [2] obtained $a_{nn} = -16.3 \pm 0.4$ fm from their nn final-state interaction (FSI) cross-section measurements made at 25 MeV using proton recoil geometry. We report the preliminary results of a new determination of $a_{nn}$ at 19 MeV at TUNL made using the neutron-deuteron breakup reaction in recoil proton geometry. The recoil proton and one of the outgoing neutrons were detected in coincidence and their energies were measured using time-of-flight techniques. Details of the experiment, analysis, and preliminary results will be presented. [1]$ D.E. Gonz$\acute{a}$lez Trotter {\it et al}., Phys. Rev. C~{\bf 73}, 034001 (2006). [2] V.H. Huhn {\it et al}., Phys. Rev. Lett.~{\bf 85}, 1190 (2000). [Preview Abstract] |
Friday, November 13, 2009 11:09AM - 11:21AM |
HC.00003: Simulation comparisons between Geant4 and MCNPX Jeromy Tompkins, Grayson Rich, Charles Arnold Geant4 and MCNPX are mainstream Monte Carlo simulation packages that are heavily used in nuclear physics research. These are tools to optimize the design of experiments and to complement the analysis of the measured data. Both codes have been utilized to model the response of a neutron counter composed of 18 $^3$He proportional counting tubes embedded in a polyethylene moderator. This work is integral to the results of neutron counting experiments conducted at the Triangle Universities Nuclear Laboratory (TUNL) in nuclear astrophysics, nuclear structure, and applied nuclear physics. The output of these simulations comparing the two packages will be discussed. [Preview Abstract] |
Friday, November 13, 2009 11:21AM - 11:33AM |
HC.00004: Further confirmation of octupole deformation in $^{144}$Ba W.A. Yzaguirre, J.H. Hamilton, S.H. Liu, A.V. Ramayya, J.K. Hwang, Y.X. Luo, J.O. Rasmussen, S.J. Zhu The energy levels in $^{144}$Ba have been studied with our high statistics $5.7 \times 10^{11}$ triple- and higher- fold coincidence data taken with Gammasphere. There are reinforcing shell gaps for $\beta _2= 0.13$ for $Z=56$ and $Z=88$, so octupole deformation is expected in $^{144}$Ba. The even parity ground state band is seen to high spin with crossing $E1$ transitions from an odd spin, negative parity band earlier, the expected $s_i=1$ band. Limited evidence for the expected $s_i=-1 $ band with the same spins and opposite parities has been reported. $s_i=-1$ band has been clearly established now with the expected crossing transitions between the even and odd spins members. In addition, numbers of new crossing transitions in the $s_i=1$ band and between the $s_i=-1$ band and $+1$ are seen. These data firmly established the octupole deformation of $^{144}$Ba. Work supported by the U.S. Department of Energy under Grants and Contract Nos. DE-FG05-88ER40407 and DE-AC03- 76SF00098. [Preview Abstract] |
Friday, November 13, 2009 11:33AM - 11:45AM |
HC.00005: Identification of high spin states in $^{134}$I from $^{252}$Cf fission S.H. Liu, J.H. Hamilton, A.V. Ramayya, J.K. Hwang, Y.X. Luo, J.O. Rasmussen, S.J. Zhu High spin states in $^{134}$I have been identified for the first time based on measurements of prompt gamma rays from the spontaneous fission of $^{252}$Cf at Gammasphere. Five excited levels with five deexciting transitions have been observed. The mass number was assigned based on the intensity of transitions in the complementary Rh fragments. It is likely that the observed yrast cascade of $^{134}$I is built on the 316.3 keV $8^-$ isomeric state with a configuration of $\pi$(1g$_{7/2}$) $\nu$(1h$_{11/2}$)$^{-1}$ based on the systematics of the ground states and isomeric states in $^{132}$I, $^{136}$I, $^ {132}$Sb and $^{136}$Cs. Angular correlations for the first two transitions in $^{134}$I and for high spin states in $^{133, 135, 136}$I were performed, but were not sufficient to firmly assign the spins and parities in $^{134}$I. A. Covello and his collaborators have prepared a paper on shell model calculations for $^{134}$I. Their results are 0 ($8^-$), 1022 ($10^-$), 1674 ($11^-$), 1905 ($12^-$), 2439 ($13^-$), and 3142 keV ($14^-$) energies, which are in good agreement with all the level energies reported here. Details of this work will be presented. Work supported by the U.S. Department of Energy under Grants and Contract Nos. DE-FG05-88ER40407 and DE-AC03-76SF00098. [Preview Abstract] |
Friday, November 13, 2009 11:45AM - 11:57AM |
HC.00006: Multiple pairing gap structures in rare earth nuclei W.D. Kulp Detailed experimental studies using multiple spectroscopic techniques reveal two extensive families of rotational bands in $^{152}$Sm that are remarkably similar. This result suggests that there are two coexisting shapes which strongly mix. Experimental results and a prescription of two-state mixing calculations are presented which describe the level energies of the ground-state and first excited ($0^+$ state) rotational bands, electric monopole transition rates, electric quadrupole matrix elements, and the isomer shift of the first excited $2^+$ state. [Preview Abstract] |
Friday, November 13, 2009 11:57AM - 12:09PM |
HC.00007: Rare Earth Metal Silicides and exotic Nuclei Richard Kriske The use of Rare Earth Metal Silicides has been seen in thermal detection since World War II. What results can be expected when Rare Earths are used with certain isotopes? More to the point can exotic isotopes of Rare Earths be made from what is known more recently about Hadrons and their construction? What if anything can be gained from manipulating isotopes with a more recent theory than that known around World War II? [Preview Abstract] |
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