Bulletin of the American Physical Society
2013 Fall Meeting of the APS Division of Nuclear Physics
Volume 58, Number 13
Wednesday–Saturday, October 23–26, 2013; Newport News, Virginia
Session ND: Nuclear Structure IV |
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Chair: Philippe Collon, University of Notre Dame Room: Grand Ballroom IV |
Saturday, October 26, 2013 8:30AM - 8:42AM |
ND.00001: Quenching of Cross Sections in Nucleon Transfer Reactions B.P. Kay, J.P. Schiffer, S.J. Freeman From a set of experiments on nucleon transfer analysed in a consistent way, we conclude that the quenching of single-particle strength that had been seen in $(e,e'p)$ reactions appears to be a more general phenomenon and is present in nucleon transfer reactions. Absolute cross sections from reactions on targets between $^{16}$O and $^{208}$Pb have been reduced to spectroscopic factors in a consistent analysis using the distorted wave Born approximation and modern global optical-model potentials. Of the 124 cases analysed, the average quenching factor is found to be 0.55 with an rms spread of 0.10, consistent with what was seen in the proton knockout $(e,e'p)$ work. It appears to be independent of target mass, reaction type, and angular momentum transfer. This work is supported by the US Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357, and the UK Science and Technology Facilities Council. [Preview Abstract] |
Saturday, October 26, 2013 8:42AM - 8:54AM |
ND.00002: Stretched states in $^{12,13}$B from the $^{14,15}$C(d,$\alpha)^{12,13}$B reactions A.H. Wuosmaa, S. Bedoor, J.C. Lighthall, S.T. Marley, D.V. Shetty, J.P. Schiffer, M. Albers, M. Alcorta, S. Almarez-Calderon, B.B. Back, C.R. Hoffman, R.C. Pardo, K.E. Rehm, P.F. Bertone We have studied the $^{14,15}$C(d,$\alpha)^{12,13}$B reactions in inverse kinematics using HELIOS (the HELIcal Orbit Spectrometer) at Argonne National Laboratory. It is known that the (d,$\alpha$) and ($\alpha$,d) reactions are highly selective and strongly populate states where the transferred proton and neutron are transferred from, or to the same shell-model orbitals with aligned spins coupled to the maximum possible angular momentum (``stretched states'') and $T_{np}$=0. For exotic nuclei studied with radioactive beams, this reaction accesses states at high spin and excitation energy otherwise inaccessible with knockout or single-nucleon transfer. Beams of 17.1 MeV/u $^{14}$C, and 15.7 MeV/u $^{15}$C made using the In-Flight production method, bombarded CD$_2$ targets. Alpha particles were detected in the HELIOS position-sensitive silicon-detector array at forward laboratory angles. Heavy beam-like recoils were detected in coincidence using silicon $\Delta$E-E telescopes also at forward angles. Evidence for strongly populated unbound states in $^{12,13}$B with possible fully aligned character will be presented. [Preview Abstract] |
Saturday, October 26, 2013 8:54AM - 9:06AM |
ND.00003: Study of the $^{15}$C($d$, $^3$He)$^{14}$B Reaction S. Bedoor, A.H. Wuosmaa, J.C. Lighthall, S.T. Marley, D.V. Shetty, M. Albers, M. Alcorta, S. Almaraz-Calderon, B.B. Back, C.R. Hoffman, R.C. Pardo, K.E. Rehm, P.F. Bertone We have studied the $^{14}$B nucleus employing the $^{15}$C(d,$^3$He)$^{14}$B reaction in inverse kinematics using HELIOS (the HELIcal Orbit Spectrometer) at the ATLAS facility at ANL. A $^{15}$C beam was produced using the In-Flight method. The $^3$He particles were detected with HELIOS. The recoiling $^{13,~14}$B nuclei were identified in a set of silicon $\Delta$E--E telescope, distinguishing bound and unbound states in $^{14}$B. From a previous study of the $^{13}$B(d, p)$^{14}$B reaction the (2$_1$,1$_1$)$^-$ states were found to be admixtures of $\ell$ = 0 and $\ell$ = 2 made up of $\pi$(0$p_{3/2}$)$^{-1}$--$\nu$(1$s_{1/2}$) and $\pi$(0$p_{3/2}$)$^{-1}$--$\nu$(0$d_{5/2}$) configurations. The (2$_2$,1$_2$)$^-$ excited states were not observed. A complementary reaction can identify the (2$_2$,1$_2$)$^-$ states in order to track the single particle strength in $^{14}$B. In the current study, proton removal from $^{15}$C explores only the $\pi$(0$p_{3/2}$)$^{-1}$--$\nu$(1$s_{1/2}$) component of states in $^{14}$B. The results provide a determination of 2$^-_2$ energy level and better constrain the 1$s_{1/2}$ and 0$d_{5/2}$ effective single--particle energies in $^{14}$B. [Preview Abstract] |
Saturday, October 26, 2013 9:06AM - 9:18AM |
ND.00004: ABSTRACT WITHDRAWN |
Saturday, October 26, 2013 9:18AM - 9:30AM |
ND.00005: One-Neutron Transfer Study of $^{133}$Sn and $^{209}$Pb by Particle-$\gamma$ Coincidence Spectroscopy J.M. Allmond, A. Galindo-Uribarri, A.E. Stuchbery, J.R. Beene, R.L. Varner, E. Padilla-Rodal, D.C. Radford, A. Ayres, A. Bey, J.C. Batchelder, C.R. Bingham, M.E. Howard, K.L. Jones, J.F. Liang, B. Manning, P.E. Mueller, S.D. Pain, W.A. Peters, A. Ratkiewicz, K.T. Schmitt, D. Shapira, M.S. Smith, N.J. Stone, C.-H. Yu A one-neutron transfer study of $^{133}$Sn and $^{209}$Pb by particle-$\gamma$ coincidence spectroscopy is presented. The selectivity of one-neutron transfer is employed to probe single-neutron states outside of the radioactive $^{132}$Sn and stable $^{208}$Pb double-magic nuclei, which are analogous to single electrons outside of closed atomic shells (i.e., alkali metals). These recent experiments were conducted at HRIBF-ORNL using a CsI-HPGe detector array (BareBall-CLARION) to detect scattered particles and emitted $\gamma$ rays from the $^9$Be($^{132}$Sn,$^8$Be)$^{133}$Sn and $^9$Be($^{208}$Pb,$^8$Be)$^{209}$Pb direct reactions. Decay paths, level energies, cross sections, and excited-state lifetimes are determined and compared to shell-model expectations. [Preview Abstract] |
Saturday, October 26, 2013 9:30AM - 9:42AM |
ND.00006: High-resolution single-neutron transfer measurements in $^{131}$Sn A. Bey, K.L. Jones, A. Ayres, S.H. Ahn, J.M. Allmond, D.W. Bardayan, A. Galindo-Uribarri, J.F. Liang, C.D. Nesaraja, D.C. Radford, S.D. Pain, S.T. Pittman, D. Shapira, K.T. Schmitt, M.S. Smith, D.W. Stracener, R.L. Varner, R.L. Kozub, R. Garcia-Ruiz, M.E. Howard, B.M. Manning, P.D. O'Malley, A. Ratkiewicz, M. Matos, E. Padilla-Rodal The r-process accounts for the production of approximately half of the elements heavier than iron, but most of the (n,$\gamma)$ cross-sections are unknown. Near shell-closures, the level density becomes low in neutron-rich nuclei and the process is dominated by direct neutron capture involving primarily shell model orbitals. Precise information on these states is essential to reduce uncertainties in nucleosynthesis models. Below the N$=$82 shell, a large amount of $^{130}$Sn accumulates at late times of the freeze-out, and subsequent individual captures are predicted to influence the final abundance distribution. Spectroscopic studies of $^{131}$Sn have been performed at HRIBF using the ($^{9}$Be,$^{8}$Be-$\gamma)$ and ($^{13}$C,$^{12}$C-$\gamma)$ reactions with a 4MeV/u $^{130g,m}$Sn beam. Channel selectivity was obtained by measuring particle-$\gamma $ coincidences in the HyBall and CLARION arrays. Strongly populated single-neutron excitations were identified and a detailed level structure of $^{131}$Sn has emerged, including the yrast structure arising from neutron transfer onto the 7$^{-}$ isomer of $^{130}$Sn. Details and results of the experiments will be presented. [Preview Abstract] |
Saturday, October 26, 2013 9:42AM - 9:54AM |
ND.00007: Evolution of Single-Neutron States in Tin Isotopes B. Manning, J.A. Cizewski, R.L. Kozub, S. Ahn, J.M. Allmond, D.W. Bardayan, J.R. Beene, K.Y. Chae, K.A. Chipps, A. Galindo-Uribarri, M.E. Howard, K.L. Jones, J.F. Liang, M. Matos, C.D. Nesaraja, P.D. O'Malley, S.D. Pain, E. Padilla-Rodal, W.A. Peters, S.T. Pittman, D.C. Radford, A. Ratkiewicz, K.T. Schmitt, D. Shapira, M.S. Smith The (d,p) reaction was measured with the radioactive ion beams of $^{126,128}$Sn in inverse-kinematics at the Holifield Radioactive Ion Beam Facility at ORNL, utilizing the SuperORRUBA silicon detector array. Reaction protons were measured for states above the N=82 shell closure in $^{127,129}$Sn. In order to obtain more precise energy levels, particle-gamma coincidence data were acquired for ($^{9}$Be,$^{8}$Be$\gamma$) in inverse-kinematics at the HRIBF using a HPGe and CsI array (CLARION+BareBall). Cross-sections, angular momentum transfers, and spectroscopic information will be presented. The present work will be combined with previous studies to complete the set of (d,p) studies on even mass tin isotopes from doubly-magic $^{132}$Sn to stable $^{124}$Sn. [Preview Abstract] |
Saturday, October 26, 2013 9:54AM - 10:06AM |
ND.00008: Collinear laser spectroscopy on neutron-deficient K isotopes K. Minamisono, B.R. Barquest, G. Bollen, D. Tarazona, A. Klose, P.F. Mantica, D.J. Morrissey, M. Hughes, R. Ringle, J.A. Rodriguez, D.M. Rossi, C.A. Ryder, S. Schwarz, R. Strum, C. Sumithrarachchi, C. Geppert The monotonic change of charge radii of K isotopes across $N$ = 20 suggests a reduction of the shell gap. We plan a systematic study of the charge radii and ground state magnetic and quadrupole moments of neutron-deficient $^{35-38}$K isotopes at the BEam COoling and LAser spectroscopy (BECOLA) facility at NSCL/MSU to investigate this anomalous behavior. The first on-line measurement at BECOLA has been for $^{38}$K, which was produced by fragmentation of a $^{40}$Ca beam, thermalized in the ANL linear gas cell, extracted at an energy of 30 keV, and transported to BECOLA. The $^{38}$K ion beam was cooled and bunched, and neutralized in a Na vapor cell. Laser-induced fluorescence was detected as a function of the Doppler-tuned laser frequency and time relative to the release of the beam bunch. [Preview Abstract] |
Saturday, October 26, 2013 10:06AM - 10:18AM |
ND.00009: New Analysis of Levels in $^{151}$Pr E.H. Wang, J.H. Hamilton, A.V. Ramayya, J.K. Hwang, A. Navin, M. Rejmund, A. Lemasson, S. Bhattacharyya, S.H. Liu, N.T. Brewer, Y.X. Luo, J.O. Rasmussen, S.J. Zhu, G.M. Ter-Akopian, Yu. Oganessian The previous reported levels and assignments to $^{151,152}$Pr [1,2] have recently been called into question [3] about the mass assignment of the reported bands [1,2]. Recently prompt gamma-rays in coincidence with isotopically-identified fission fragments using VAMOS$++$ and EXOGAM, produced using $^{238}$U on a $^{9}$Be target, at an energy around the Coulomb barrier have been reported. [4]. We have combined the $\gamma -\gamma -\gamma -\gamma $ data from $^{252}$Cf (SF) and those from the in beam mass- and Z-gated spectra to assign transitions and levels in $^{151}$Pr. In contrast to [3], the transitions previously assigned to $^{151}$Pr are all seen in the M-Z gated spectra. In addition, all the transitions in both bands previously assigned to $^{152}$Pr [2] are also seen in the $^{151}$Pr M-Z gated spectra but not in the $^{152}$Pr M-Z gated spectrum. Hence all four bands are now assigned to $^{151}$Pr. The new level scheme in $^{151}$Pr will be presented.\\[4pt] [1] J. K. Hwang \textit{et al.}, Phys. Rev. C~\textbf{82}, 034308 (2010).\\[0pt] [2] S. H. Liu \textit{et al.}, Phys. Rev. C~\textbf{84}, 044303 (2011).\\[0pt] [3] T. Malkiewicz \textit{et al.}, Phys. Rev. C~\textbf{85}, 044314 (2012). [4] A. Navin et al. (submitted); A. Navin, 5th Int. Conf. on~\textit{Fission and properties of neutron-rich nuclei, Sanibel 2012}, World Scientific, in press. [Preview Abstract] |
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