Bulletin of the American Physical Society
2007 APS April Meeting
Volume 52, Number 3
Saturday–Tuesday, April 14–17, 2007; Jacksonville, Florida
Session J8: Structure and Decay of Heavy Nuclei |
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Sponsoring Units: DNP Chair: Jolie Cizewski, Rutgers University Room: Hyatt Regency Jacksonville Riverfront City Terrace 4 |
Sunday, April 15, 2007 10:30AM - 10:42AM |
J8.00001: Highly Deformed Shape Structure in $^{160,161}$Tm C. Teal, K. Lagergren , M.A. Riley, A. Aguilar, M.P. Carpenter, U. Garg, G.B. Hagemann, D.A. Hartley, D.T. Joss, R.V.F. Janssens, F.G. Kondev, T. Lauritsen, C.J. Lister, E.F. Moore, S.W. $\O$deg\"{a}rd, G. Sletten, X. Wang, S. Zhu The recent discovery of four rotational bands displaying characteristics of triaxial superdeformation (TSD) in $^{157,158}$Er bands has opened a new high spin dominion near N$\sim$90 in the rare-earth region [1]. However, evidence on neighboring nuclei is necessary to develop a more complete understanding of this phenomenon. In an experiment performed at the Argonne Tandem Linear Accelerator System (ATLAS) using the Gammasphere detector array, similar highly deformed band(s) in $^{160,161}$Tm have been found and will be discussed. [Preview Abstract] |
Sunday, April 15, 2007 10:42AM - 10:54AM |
J8.00002: The Nuclear Structure of the High-Spin States of the $^{134}$Ba and $^{135}$Ba Nuclei. nd $^{135}$Ba Nuclei. W.T. Cluff, M.A. Riley, A. Aguilar, I. Calderin, D. Campbell, E. Diffenderfer, J. Fridmann, T. Hinners, J. Pavan, P. Pipidis, C. Teal, M. Wiedeking The high-spin states of the $^{134}$Ba and $^{135}$Ba nuclei have been studied using the $^{124}$Sn+$^{14}$C reaction at beam energies of 57 and 50 MeV respectively. The $^{14}$C ion beam, a distinguishing feature of the FSU(Florida State University) Superconducting Linear Accelerator Laboratory, when paired with the most neutron rich stable isotope of Sn currently gives an optimal means of observing these nuclei at high spin. The $\gamma$ rays from this reaction were detected by the FSU Compton Suppressed Hyperpure Ge Detector Array. Confirmed spin states of 14$\hbar$ have been seen for $^{134}$Ba and spin states of 35/2$\hbar$ have been seen for $^{135}$Ba. Their level schemes shall be presented and their analysis and interpretation will be discussed. [Preview Abstract] |
Sunday, April 15, 2007 10:54AM - 11:06AM |
J8.00003: A Detailed Study of Odd-Odd $^{170}$Ta Approaching Spin 50 $\hbar$ A. Aguilar, M.A. Riley, C. Teal, K. Lagergren, D.J. Hartley, W.H. Mohr, J.R. Vanhoy, R.V.F. Janssens, M.P. Carpenter, A.A. Hecht, T. Lauritsen, E.F. Moore, S. Zhu, F.G. Kondev, M.K. Djongolov, M. Danchev, L.L. Riedinger, G.B. Hagemann, G. Sletten, P. Chowdhury, S.K. Tandel, W.C. Ma, S.W. $\O$deg\"{a}rd High-spin states of the odd-odd nucleus $^{170}$Ta were studied via the $^{124}$Sn ($^{51}$V, 5n) fusion-evaporation reaction. Data were collected by the Gammasphere spectrometer and sorted into $\gamma$-$\gamma$-$\gamma$ cubes and $\gamma$-$\gamma$-$\gamma$-$\gamma$ hypercubes for detailed analysis. Over four hundred new gamma-ray transitions were discovered along with twenty new bands. The relative spins and excitation energies of all the rotational structures were also determined for the first time. These exceptional data allowed for one of the most comprehensive investigations of any odd-odd nucleus while observing spins approaching 50 $\hbar$. [Preview Abstract] |
Sunday, April 15, 2007 11:06AM - 11:18AM |
J8.00004: Using $^{171,173}$Yb($d,p\gamma$) to benchmark a surrogate reaction for neutron capture R. Hatarik, J.A. Cizewski, T. Swan, S.D. Pain, P.D. O'Malley, D.W. Bardayan, L.A. Bernstein, J.T. Burke, F.S. Dietrich, J.E. Escher, M.S. Johnson, J. Gibelin, L. Phair, R.L. Kozub, A. Kronenberg An indirect approach to measure neutron capture cross sections on unstable nuclei is the surrogate reaction method, which makes it possible to relate the desired cross section to a cross section of an alternate reaction that proceeds through the same compound nucleus. To test the feasibility of using a ($d,p\gamma$) reaction as a surrogate, a benchmark experiment has been carried out with the goal to reproduce the known neutron capture cross section ratio of $^{171}$Yb and $^{173}$Yb. The $^{171,173}$Yb($d,p\gamma$) reactions were measured using an 18.5 MeV deuteron beam from the 88-Inch Cyclotron at LBNL. Reaction protons were detected using the Si detector array STARS and 6 Clover detectors (LIBERACE) were used to measure coincident $\gamma$-rays. Preliminary results of this measurement will be presented. [Preview Abstract] |
Sunday, April 15, 2007 11:18AM - 11:30AM |
J8.00005: ABSTRACT WITHDRAWN |
Sunday, April 15, 2007 11:30AM - 11:42AM |
J8.00006: Decay spectroscopy of the lightest proton-emitting Re isotopes Iain Darby, David Joss, Robert Page, Juha Uusitalo, John Simpson Proton emission is expected to determine the limit of experimental observation for the neutron-deficient nuclei of most elements. Proton radioactivity may be treated as a simple quantum tunnelling process through the Coulomb barrier. The barrier penetration probability (and thus the decay half- lives) for proton emitters are sensitive to the proton decay energies and the orbital angular momentum of the initial state from which emission occurs. Therefore proton radioactivity is an ideal mechanism with which to determine and characterise single-particle states beyond the proton drip line. Additionally the characteristics (short half- lives and discrete energies) of the emitted protons are ideal for tagging in $\gamma$-ray spectroscopy experiments. A decay spectroscopy experiment has been performed at the Accelerator Laboratory of the University of Jyv\"{a}skyl\"{a} (JYFL), using the RITU separator in conjuction with the GREAT focal-plane spectrometer (which possesses a high efficiency for delayed $\gamma$-rays), to study the lightest Re nuclei via the reaction $^{106}$Cd($^{58}$Ni,pxn). The first observation of the lightest known proton-emitting isotope {$^{159}$}Re will be presented. In $^{160}$Re the observation of $\gamma$-ray transitions feeding the known $d_{3/ 2}$ ground state which may account for the non-observation of particle mission from the anticipated $h_{11/2}$ isomeric state is eported. [Preview Abstract] |
Sunday, April 15, 2007 11:42AM - 11:54AM |
J8.00007: The $\beta$ decay properties of $^{83,84}$Ga J.A. Winger, S.V. Ilyushkin, K.P. Rykaczewski, C.J. Gross, D. Shapira, R. Grzywacz, S.N. Liddick, C. Mazzocchi, S. Padgett, M.M. Rajabali, J.C. Batchelder, A. Korgul, W. Krol\'{a}s, E.F. Zganjar, A. Piechazek, C. Goodin, J.H. Hamilton In an experiment at the Holifield Radioactive Ion Beam Facility, post accelerated beams were used to measure the decay properties of $^{83,84}$Ga. The high resolution isobar separator was tuned with with aid of an ion chamber to provide beams with enhanced Ga purity. The decays were observed using four Ge clover and two plastic $\beta$ detectors. In both decays, the strongest $\gamma$ rays come from the delayed-neutron branch. For $^{83} $Ga we observed for the first time the transition between the $s_{1/2}$ first excited state and the $d_ {5/2}$ ground state in $^{83}$Ge, with confirmation from the $\beta$ delayed-neutron decay of $^{84}$Ga. The energy separation between these states is much lower than suggested by an earlier particle transfer measurement. For $^ {84}$Ga, the $\gamma$ rays assigned to this decay are in contradiction with those previously published. [Preview Abstract] |
Sunday, April 15, 2007 11:54AM - 12:06PM |
J8.00008: Identification of the $^{109}$Xe $\rightarrow$ $^{105}$Te $\rightarrow$ $^{101}$Sn alpha-decay chain S.N. Liddick, R. Grzywacz, C. Mazzocchi, C.R. Bingham, G. Drafta, A. Korgul, M.N. Tantawy, R.D. Page, I.G. Darby, D.T. Joss, J. Thomson, K.P. Rykaczewski, C.J. Gross, J.C. Batchelder, C. Goodin, J.H. Hamilton, J.K. Hwang, K.. Li, S. Ilyushkin, J.A. Winget, K. Lagergren, W. Krolas, A.A. Hecht The existence of a region of alpha emitting nuclei above $^{100}$Sn is due to the presence of the Z=N=50 shell closures. The region is a fertile area to investigate possible enhanced correlations between neutrons and protons filling the same single-particle orbits and could lead to the observation of superallowed alpha decay as an approach is made towards $^{100}$Sn. Nuclear structure studies in this region are problematic due to both a low probabilty for the production of neutron-defficient isotopes and the difficulty in detecting short-lived alpha decaying nuclei. The new isotope $^{109}$Xe was produced at the HRIBF at Oak Ridge National Laboratory in the $^{58}$Ni($^{54}$Fe,3n) fusion evaporation reaction. A digital electronics aquisition system was used to identify $^{105}$Te through the $^{109}$Xe$\rightarrow ^{105}$Te $\rightarrow ^{101}$Sn alpha-decay chain. This marks the closest approach to the N = Z line above $^{100}$Sn. The superallowed character of the alpha decay of $^{105}$Te and the prospects for reaching the alpha-decay chain $^{108}$Xe$\rightarrow ^{104}$Te $\rightarrow ^{100}$Sn will be discussed. [Preview Abstract] |
Sunday, April 15, 2007 12:06PM - 12:18PM |
J8.00009: High-spin states in $^{135}$Xe N. Fotiades, R.O. Nelson, M. Devlin, J.A. Cizewski, R. Kr\"{u}cken, R.M. Clark, P. Fallon, I.Y. Lee, A.O. Macchiavelli, J.A. Becker, W. Younes, T. Ethvignot, T. Granier Investigation of high-spin states in $^{135}$Xe is important for comparison with shell-model calculations because this isotope has only one neutron hole in the N=82 shell and, hence, a relatively limited number of single-particle configurations at low excitation energies. The structure of $^{135}$Xe was studied in two experiments: i) as a fission fragment following the fission of the $^{226}$Th compound nucleus formed in a fusion-fission reaction ($^{18}$O at 91~MeV on $^{208}$Pb) with the GAMMASPHERE spectrometer at LBNL, and ii) as an evaporation residue in the $^{136}$Xe(n,2n$\gamma$)$^{135}$Xe reaction with the GEANIE spectrometer at LANL. The level scheme above the 11/2$^-$, 527-keV isomer (from the odd neutron in the $h_{11/2}$ orbital) was established up to 3710-keV excitation energy. This is the first observation of negative-parity high-spin states in this isotope. A strong sequence was assigned to $^{135}$Xe and forms the yrast decay path including the 15/2$^{-}$ and 19/2$^{-}$ states. A much weaker sequence of $\gamma$-rays was tentatively assigned to $^{135}$Xe and is a candidate for the off-yrast sequence that includes the 13/2$^{-}$ and 17/2$^{-}$ states, expected in the weak coupling of the $h_{11/2}$ neutron to the even-A core. The results are compared with predictions from shell-model calculations. [Preview Abstract] |
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