Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session CF: Nuclear Structure I |
Hide Abstracts |
Chair: Paul Fallon, Lawrence Berkeley National Laboratory Room: 104AB |
Thursday, October 27, 2011 8:30AM - 8:42AM |
CF.00001: Determining Neutron-Induced Fission Cross Sections of Picosecond States R.J. Casperson, J.T. Burke, I.J. Thompson, F.S. Dietrich, J.E. Escher, J.J. Ressler, N.D. Scielzo, E. Swanberg, W. Younes The first excited state neutron-induced fission cross section of $^{239}$Pu is not directly measurable, due to the short lifetime of the 7.86 keV 3/2+ excited state. We use recent developments in transfer reaction theory to identify the angular momentum distribution of excited states in the pre-fission nucleus $^{240}$Pu$^{*}$. This nucleus will be produced in a (d,p) reaction on $^{239}$Pu, and the fission probability as a function of outgoing proton angle and energy will be measured. By combining this measurement with (d,p) reaction theory, the fission probability of individual angular momenta can be determined, and recombined into the excited state fission probability. First experimental results will be presented. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Thursday, October 27, 2011 8:42AM - 8:54AM |
CF.00002: Lifetime and proton component of the 2$^+_1$ state in $^{16}$C Marina Petri The lifetime of the 2$^+_1$ state in $^{16}$C was measured using the Recoil Distance Method with fast radioactive beams at the National Superconducting Cyclotron Laboratory. The lifetime of 11.4$\pm$0.3 ps, corresponding to a B(E2:2$^+_1$ $\rightarrow$ 0$^+_{g.s.}$) = 4.21 $\pm$ 0.11 e$^2$fm$^4$, is in good agreement with previous values [1]. Excited states in $^{16}$C were populated via the $^9$Be($^{17}$N,$^{16}$C+$\gamma$)X one-proton knockout reaction. The one-proton knockout cross section is used to extract the proton component of the $^{16}$C 2$^+_1$ state. Gamma branching ratios between excited states were also determined. The B(E2) and branching ratios will be compared with p-sd shell model and no core shell model (with NN and NN+NNN) calculations.\\[4pt] [1] M. Wiedeking et al., Phys. Rev. Lett., 100, 152501 (2008). [Preview Abstract] |
Thursday, October 27, 2011 8:54AM - 9:06AM |
CF.00003: B(E2) Transition Strengths of Neutron-rich Carbon Isotopes in a Seniority Scheme A.O. Macchiavelli, M. Petri, P. Fallon, R.M. Clark, M. Cromaz, I-Y. Lee, S. Paschalis Lifetime measurements of $^{16,18,20}$C isotopes using the DSAM technique have been recently carried out at NSCL [1,2]. The new data provide unique information about the structure of the Carbon isotopes. In this work we attempt to interpret the derived B(E2) transitions strengths in terms of a seniority inspired scheme. The analysis shows an important role played by proton excitations due to an effective reduction of the p$_{3/2}$ -- p$_{1/2}$ spin-orbit splitting. The predicted behavior of spectroscopic factors for proton removal and magnetic moments can be tested experimentally. \\[4pt] [1] M.Petri et al. Submitted to Phys. Rev. Lett. \\[0pt] [2] P.Voss et al. to be published. [Preview Abstract] |
Thursday, October 27, 2011 9:06AM - 9:18AM |
CF.00004: Studies of transitional Gadolinium nuclei by particle-gamma coincidence techniques T.J. Ross, R.O. Hughes, C.W. Beausang, J.M. Allmond, J.T. Burke, J.E. Escher, L.W. Phair, N. Scielzo, C.T. Angell, M.S. Basunia, D.L. Bleuel, R.J. Casperson, P. Fallon, R. Hatarik, J. Munson, S. Paschalis, M. Petri, J.J. Ressler Nuclei in the N=90 transitional region have been the focus of intense study for a number of years. In spite of this, recent particle-gamma coincidence studies of $^{155}$Gd revealed inconsistencies in the present single particle assignments [1]. Expanding on these findings, an experiment was performed using the STARS-LIBERACE array at the 88-Inch Cyclotron in Lawrence Berkeley National Laboratory. A 25 MeV proton beam incident on $^{154}$Gd and $^{158}$Gd targets was used to populate states in $^{152,153,156,157}$Gd via (p,d) and (p,t) reactions. The silicon telescope STARS provided particle identification, residual nucleus energy and angular information. Coincident gamma rays were detected using the LIBERACE clover array. Details of new states identified in $^{153}$Gd and $^{157}$Gd will be presented as well as a method of extracting the spin distribution imparted to the nucleus via transfer reactions. [1] J.M. Allmond et. al. Phys. Rev. C 81 064316 (2010). \newline This work supported in part by U.S. DOE grant numbers DE-FG02-05 ER41379 \& DE-FG52-06 NA26206(University of Richmond), DE-AC52 07NA27344(LLNL) and DE-AC02 05CH11231(LBNL). [Preview Abstract] |
Thursday, October 27, 2011 9:18AM - 9:30AM |
CF.00005: Particle-$\gamma$ Spectroscopy of $^{13}$C($^{134}$Te,$^{12}$C)$^{135}$Te and $^{9}$Be($^{134}$Te,$^8$Be)$^{135}$Te: One-Neutron Transfer Study of Z=52, N=83 and the $\nu$i$_{13/2}$ State J.M. Allmond, D.C. Radford, C. Baktash, J.R. Beene, A. Galindo-Uribarri, P.A. Hausladen, J.F. Liang, J. Pavan, D. Shapira, R.L. Varner, C.-H. Yu, C.R. Bingham, M. Danchev, J.P. Urrego-Blanco, L. Chaturvedi, D. Fong, J.K. Hwang, W. Krolas A HPGe and CsI array (CLARION+HYBALL @ HRIBF) is used to study the $^{13}$C($^{134}$Te,$^{12}$C)$^{135}$Te and $^9$Be($^{134}$Te,$^8$Be)$^{135}$Te direct reactions by particle-$\gamma$ coincidence measurements. The particle-$\gamma$ technique has several advantages (particularly in inverse kinematics) which include the following: can determine decay paths by particle-$\gamma$-$\gamma$, can determine high-precision level energies, can determine multipolarities of transitions by particle-$\gamma$ angular correlations, and can infer cross sections. The use of one-neutron transfer into Z=52, N=83 is employed to gain selectivity to the single-particle neutron states outside of the N=82 shell closure. Results are presented for $^{135}$Te(Z=52,N=83); particularly, results are presented for the new $\nu$i$_{13/2}$ single-particle state at 2107 keV. [Preview Abstract] |
Thursday, October 27, 2011 9:30AM - 9:42AM |
CF.00006: Particle-Gamma Coincidence Studies of Uranium Nuclei R.O. Hughes, T.J. Ross, C.W. Beausang, J.T. Burke, N.D. Scielzo, M.S. Basunia, C.M. Campbell, R.J. Casperson, H.L. Crawford, J. Munson, L. Phair, J.J. Ressler The STARS/LIBERACE array at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory is proving to be an extremely versatile device for probing nuclear structure via (charged) particle-$\gamma$ coincidence spectroscopy. The technique enables the properties of low- and medium-spin states up to and beyond the neutron separation energy to be probed and give rare insights into the high-level density nuclear continuum well above the pair gap. Recently, $^{234}$U, $^{235}$U, $^{236}$U and $^{237}$U were studied via (p,d) and (p,t) reactions on $^{236}$U and $^{238}$U targets. The exit channel and excitation energy of the residual nucleus are selected by measuring the outgoing charged particle using the STARS silicon telescope array, while coincident gamma rays are detected with the LIBERACE clover array. The subsequent particle spectra show the ensemble of states that were directly populated by the reaction while $\gamma$-ray coincidences reveal the decay path from a given level. Results from our recent experiment will be presented. This work was supported by DoE Grant Numbers: DE-FG52-06 NA26206 and DE-FG02-05 ER41379. [Preview Abstract] |
Thursday, October 27, 2011 9:42AM - 9:54AM |
CF.00007: Testing the theoretical predictions and affirming chiral behavior in the $A\sim130$ region: Chirality in ${}^{133}Ce$ A.D. Ayangeakaa, U. Garg, S. Frauendorf, J.T. Matta, B.K. Nayak, S.S. Ghugre, M.P. Carpenter, C. Chiara, C. Hoffman, R.V.F. Janssens, F. Kondev, T. Lauritsen, C. Nair, D. Seweryniak, A. Torben, I. Stefanescu, S. Zhu Microscopic calculations based on the three dimensional Tilted Axis Cranking (TAC) model have predicted the existence of a chiral partner band to the $\pi(h{}_{11/2}g{}_{7/2})\otimes\nu(h{}_{11/2})$ band in ${}^{133}$Ce. To test this prediction, high spin states in ${}^{133}$Ce were populated with the ${}^{116}Cd({}^{22}Ne,5n) {}^{133}Ce$ fusion evaporation reaction at a beam energy of 112MeV using GAMMASPHERE. A $\Delta I=1$ candidate chiral-band partner built on the $\pi(h{}_{11/2}g{}_{7/2})\otimes\nu(h{}_{11/2})$ configuration has been observed. Details of chiral assignment to this pair of bands will be presented. [Preview Abstract] |
Thursday, October 27, 2011 9:54AM - 10:06AM |
CF.00008: 2-gamma decay of the 662-keV isomer in $^{137}$Ba D.J. Millener, R.J. Sutter, D.E. Alburger 2-gamma decay of the 662-keV $^{137}$Ba isomer following $^{137}$Cs beta decay has been observed using two 3"x3" NaI detectors, a 20.5-$\mu$Ci source, and a Pb shielding geometry designed to minimize direct and sequential Compton scattering backgrounds. In runs totaling 144 days, a 662-keV peak has been observed in the profile across the diagonal connecting 662-keV axis points in a 2-dimensional coincidence pulse-height spectrum. A preliminary value of $2.0(6)\times 10^{-6}$ is derived for the 2-gamma/1-gamma intensity ratio. The distribution of 662-keV events along the 2D diagonal is a continuum centered at 331-331 keV with a shape favoring a double quadrupole E2-M2 or M2-E2 decay sequence. Our result compares with upper limits of $< 10^{-5}$, our assessment of the Beusch experiment [1], and $< 2.2\times 10^{-6}$ by Basenko et al. [2]. It will be compared with theoretical estimates. \\[4pt] [1] W. Beusch, Helv Phys. Acta 33, 363 (1960)\\[0pt] [2] V.K. Basenko, A.N. Berlizov, and G.A. Prokopets, Bull. Russ. Acad. Sci. 56, 94 (1992) [Preview Abstract] |
Thursday, October 27, 2011 10:06AM - 10:18AM |
CF.00009: Commissioning of GRETINA tracking array, testing of delayed coincidence Aaron Sharpe, C.W. Beausang, I.Y. Lee GRETINA is new a gamma-ray tracking array currently being commissioned at LBNL. When complete, GRETINA will consist of seven quad-modules. Each quad-module in turn consists of four large volume 36 fold segmented Ge crystals. The segmentation of the crystals, together with digital pulse processing techniques allows the position of individual gamma-ray interactions in the detector to be determined. As part of the commissioning process, a series of engineering runs was carried out in the spring at LBNL to check various aspects of the detector performance under ``battle conditions.'' One of these runs involved testing delayed coincidence cability by the measurement of the lifetimes of several high-K isomers in Hafnium-176. Medium/high-spin states in 176Hf were populated following the 176Yb($\alpha$,4n) reaction at a beam energy of 41 MeV. Data was taken over a two day period using a variety of trigger conditions. Data analysis is ongoing and initially focused on the 1559 keV and 1333 keV isomers. Preliminary results, which are in agreement with the previously accepted lifetimes, will be presented. This work was partly supported by the US Department of Energy under contact number DE- AC02-05CH11231 and grant numbers DE-FG52-06 NA26206 and DE-FG02-05 ER41379. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700