Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session DG: Deformed Nuclei and the Heaviest Elements |
Hide Abstracts |
Sponsoring Units: DNP JPS Chair: Peter Moller, Los Alamos National Laboratory Room: Ritz-Carlton Hotel Plantation 2 |
Tuesday, September 20, 2005 7:00PM - 7:15PM |
DG.00001: Strongly deformed structures in $^{172,171}$Hf W.C. Ma, Y. Zhang, E. Ngijoi-Yogo, D.G. Roux, J.A. Winger, R.B. Yadav, M.P. Carpenter, R.V.F. Janssens, T.L. Khoo, F.G. Kondev, T. Lauritsen, E.F. Moore, S. Zhu, D.J. Hartley, D. Cullen, S.V. Rigby, D.T. Scholes, P. Chowdhury, S. Odegard, M.K. Djongolov Three possible strongly deformed (SD) bands in $^{172}$Hf and one in $^{171}$Hf were identified from our recent Gammasphere experiment at ANL using the $^{48}$Ca($^{128}$Te, xn) reactions at 209 MeV. Further, the band in $^{171}$Hf has been linked to the known normal deformed structures. The spin/parity of levels in this band as well as other properties, such as the alignment and excitation energy, could be determined, and the intrinsic quasiparticle configuration of the band proposed. The wobbling mode, a characteristic motion of triaxial nuclei originally predicted for even-even nuclei, has been established in $^ {161,163,165,167}$Lu (Z=71). The SD bands observed in several Hf isotopes appear to be quite different from the triaxial strongly deformed (TSD) bands in Lu isotopes. Possible difference of high- j intruder orbitals involved in these excitations will be discussed. [Preview Abstract] |
Tuesday, September 20, 2005 7:15PM - 7:30PM |
DG.00002: Re-interpretation of the structure of $^{184}$Pt R.B. Cakirli, E.A. McCutchan, R.F. Casten, H. Ai, C.R. Fitzpatrick, G. Gurdal, A. Heinz, J. Qian, R. Winkler The traditional interpretation of the light Pb, Hg and Pt isotopes invokes the concept of proton intruder states from above the Z=82 shell gap. However, recently, a single configuration IBA-1 Hamiltonian was used to test this interpretation of the light Pt isotopes [1]. Without any need for intruder states, these results showed excellent agreement in both energies and B(E2) values. Among these Pt isotopes, $^{184}$Pt lacks sufficient data on relative B(E2) values. Therefore, to obtain further information on this nucleus, we carried out a $\beta$-decay experiment at the Yale Moving Tape Collector at WNSL using the $^{175}$Lu ($^{16}$O,7n) reaction at 132MeV. After producing parent $^{184}$Au, we observed transitions in $^{184}$Pt particularly those from low-spin non-yrast states were observed using clover detectors from YRAST Ball. The results of this work will be discussed. This work was supported by US DOE Grant No.DE-FG02-91ER-40609 \\ \\ \mathbb{[1]} E.A. McCutchan, R.F. Casten, and N.V. Zamfir, Phys.Rev.C (in press). [Preview Abstract] |
Tuesday, September 20, 2005 7:30PM - 7:45PM |
DG.00003: Shape transitions in neutron-rich Ru isotopes: spectroscopy of $^{109,110,111,112}$Ru C.Y. Wu, H. Hua, D. Cline, A.B. Hayes, R. Teng, D. Riley, R.M. Clark, P. Fallon, A. Goergen, A.O. Macchiavelli, K. Vetter The spectroscopy of neutron-rich $^{109,110,111,112}$Ru nuclei was studied by measuring the prompt $\gamma $ rays originated from fission fragments, produced by the $^{238}$U($\alpha $,f) fusion-fission reaction, in coincidence with the detection of both fragments. For $^{109,111}$Ru, both the negative-parity ($h_{11/2}$ orbitals) and positive-parity ($g_{7/2}$ and/or $d_{5/2}$ orbitals) bands were extended to substantial higher spin and excitation energy than known previously. The ground-state and $\gamma $-vibrational bands of $^{110,112}$Ru also were extended to higher spin. This extension allowed observation of the second band crossing at a rotational frequency of $\approx $450 keV in $^{112}$Ru, which is $\approx $50 keV above the first band crossing. At a similar rotational frequency, the first band crossing for the $h_{11/2}$ band in $^{111}$Ru was observed, which is absent in $^{109}$Ru. These band crossings most likely are caused by the alignment of the $g_{9/2}$ proton pair. This early onset of the band crossing for the aligned $\pi g_{9/2}$ orbitals may be evidence of a triaxial shape transition from prolate to oblate occurring in $^{111}$Ru. The data, together with the comparison of calculations of the cranked shell model, will be presented. Work supported in part by DOE under contracts no. W-7405-ENG-48 (UC-LLNL) and DE-AC03-76SF00098 (UC-LBNL). Work at University of Rochester supported by NSF and AFOSR. [Preview Abstract] |
Tuesday, September 20, 2005 7:45PM - 8:00PM |
DG.00004: A New isomeric State in $^{116}$Ag J.C. Batchelder, H.K. Carter, E.H. Spejewski, A. Piechaczek, E.F. Zganjar, J.C. Bilheux, K.P. Rykaczewski, D.W. Stracener, W.D. Kulp, J.L. Wood, C.R. Bingham, R. Grzywacz, Y. Larochelle, M.N. Tantawy, D.J. Hartley, J.A. Winger, D.J. Fong, J.H. Hamilton, J.K. Hwang, W. Krolas, A.V. Ramayya, P.E. Garrett We have discovered a new isomer in $^{116}$Ag with a half-life of 20(1) seconds, through the use of conversion electron, beta and gamma spectroscopy of on-line mass separated radioactivities at the Holifield Radioactive Ion Beam Facility at ORNL. The observed electron peaks at 22.5, 44.42, and 47.33 keV were interpreted as the K, L, and M conversion electron lines resulting from a 47.9 keV E3 transition associated with the decay of a second isomeric level in $^{116}$Ag. A new level structure of $^{116}$Ag is proposed, with the levels identified as the 0$^-$ ground-state and isomeric levels at 47.9 and 128.8 keV assigned spin/parities of 3$^+$ and 6$^-$ respectively. Nilsson configurations proposed for these isomeric levels correspond to an oblate deformation of $^{116}$Ag. [Preview Abstract] |
Tuesday, September 20, 2005 8:00PM - 8:15PM |
DG.00005: New results on shape coexistence in the light Pb region Janne Pakarinen Experimental evidence for shape-coexisting configurations has been observed in Pb isotopes close to the neutron mid-shell. These structures intrude down to energies close to the spherical ground state and can be associated with intruder 2$p$-2$h$ and 4$p$-4$h$ proton shell-model excitations across the $Z$=82 energy gap [1], resulting in a unique shape-triplet in $^{186}$Pb [2]. In-beam $\gamma$$\gamma$ coincidence data have been collected for $^{186}$Pb by combining the JUROGAM Ge-detector array and the GREAT spectrometer with the RITU gas-filled recoil separator for Recoil-Decay Tagging measurements. In addition to the known prolate yrast band in $^{186}$Pb, these data have enabled three new bands to be identified [3]. Complementary results were provided in Recoil Distance Doppler-Shift lifetime measurements, where the electromagnetic transition properties of the lowest yrast states were measured [4]. In this contribution, the results of latest experiments employing these techniques will be presented and their implications for intruder structures will be discussed.\newline \newline [1] W. Nazarewicz, Phys.\ Lett.\ B {\bf 305}, 195 (1993).\newline [2] A. Andreyev, Nature {\bf 405}, 430 (2001).\newline [3] J. Pakarinen \textit{et. al.}, Submitted to Phys.\ Rev.C.\newline [4] T. Grahn, Private Communications. [Preview Abstract] |
Tuesday, September 20, 2005 8:15PM - 8:30PM |
DG.00006: Delayed nucleon alignment and search for prolate-to-oblate shape transition in $^{180}$Hf at high spins* U.S. Tandel, P. Chowdhury, S.K. Tandel, S. Sheppard, D. Cline, C.Y. Wu, M.P. Carpenter, R.V.F. Janssens, T.L. Khoo, T. Lauritsen, C.J. Lister, D. Seweryniak, S. Zhu Early calculations predict a giant backbend in $^{180}$Hf at I$\approx $26$\hbar $ due to a crossing of two bands with different intrinsic shapes [1]. More recent cranking calculations [2,3] predict that oblate collective rotational states coexist with prolate ones in neutron-rich Hf nuclei, with the oblate becoming yrast at higher spins. The first nucleon alignment in $^{180}$Hf, predicted at $\hbar $$\omega $$\approx $0.35 MeV, was not observed in recent studies up to the $\hbar $$\omega$$\approx $0.43 MeV [3]. In the present work, high spin states in $^{180}$Hf were populated by inelastic excitation, with a 1300 MeV $^{180}$Hf beam from the ATLAS accelerator at Argonne incident on a thin $^{232}$Th target. The recoiling beam- and target-like nuclei were identified using the position-sensitive detector CHICO, which allowed event-by-event Doppler correction for the $\gamma $-rays emitted in flight by the recoiling nuclei and detected with the Gammasphere array. The extended level scheme of $^{180}$Hf will be discussed in the context of the predicted alignments and shape changes. [1] R.R. Hilton and H.J. Mang, Phys. Rev. Lett. 43, 1979 (1979). [2] F.R. Xu et al., Phys. Rev. C62, 014301 (2000). [3] E. Ngijoi-Yogo, Ph.D. thesis, U.Mass. Lowell (2004)\\ $*$Supported by US Department of Energy Grants DE-FG02-94ER40848, W-31-109-ENG-38 and the National Science Foundation. [Preview Abstract] |
Tuesday, September 20, 2005 8:30PM - 8:45PM |
DG.00007: On effects of K-mixing in wobbling motion Julian Fletcher, Makito Oi Bohr and Mottelson showed that a quantum rotor with triaxiality shows wobbling motion at high spin under the classical condition, $I \simeq I_1$. Quantum mechanically, we need to reconsider this condition as $I \simeq \langle\hat{I}_1\rangle$ because the Hamiltonian does not commute with $I_1$. In other words, when we call eigenvalues of the angular momentum operator $I_1$ $K$-quantum numbers, $K$ is not a good quantum number in this model. We discuss several effects of $K$-mixing in the wobbling model, and present an view about how the wobbling motion should be understood quantum mechanically. [Preview Abstract] |
Tuesday, September 20, 2005 8:45PM - 9:00PM |
DG.00008: Production and Decay of Light Thorium Isotopes J. Qian, A. Heinz, R. Winkler, R.V.F. Janssens, D. Peterson, D. Seweryniak, B. Back, M.P. Carpenter, A. Hecht, C.-L. Jiang, F.G. Kondev, T. Lauritsen, C.J. Lister, S. Zhu, P. Collon, X. Wang, N. Hoteling A beam of $^{50}_{22}$Ti at 230 MeV, accelerated by the Argonne Tandem Linac Accelerator System (ATLAS), was incident on a $^ {170}_{68}$Er target. Recoils from fusion-evaporation reactions were separated using the Fragment Mass Analyzer (FMA) according to their mass-to-charge ratio. The recoil position was detected with a Proportional Grid Avalanche Counter (PGAC) and subsequently implanted in a Double-sided Silicon Strip Detector (DSSD) located at the focal plane of FMA. Position and time of implant events and subsequent alpha decays were measured and correlated. An array of gamma detectors surrounding the DSSD was used for the correlation of alpha and gamma decays. A beam monitor detector provided a measurement of the beam current, allowing the determination of production cross sections. The experimental setup and results will be presented. This work has been supported by the DOE under grant number DE-FG02-91ER-4069 and W-31-109-ENG-38 [Preview Abstract] |
Tuesday, September 20, 2005 9:00PM - 9:15PM |
DG.00009: $\gamma $-rays from the decay of the 0.26 s isomer in $^{254}$No* S.K. Tandel, T.L. Khoo, D. Seweryniak, P. Chowdhury, U.S. Tandel, I. Ahmad, B. Back, M.P. Carpenter, C.N. Davids, A. Hecht, R.V.F. Janssens, F.G. Kondev, T. Lauritsen, C.J. Lister, E.F. Moore, D. Peterson, X.F. Wang, S.F. Zhu, G. Mukherjee, A. Heinz, P. Reiter, P.A. Butler, R. Herzberg, G. Jones The t$_{1/2}$=0.26 s, high-K isomer in $^{254}$No, first identified by Ghiorso et al. and further studied by Mukherjee et al. through the detection of electrons, was populated using the $^{208}$Pb($^{48}$Ca,2n) reaction at a beam energy of 219 MeV, provided by the ATLAS accelerator at Argonne. The evaporation residues were transported through the Fragment Mass Analyzer (FMA), identified by mass and then implanted in a 40x40 mm Double-Sided Silicon Strip Detector (DSSD). Conversion electrons following the de-excitation of the isomer and $\alpha $-particles from $^{254}$No were detected, with the requirement that all signals originate from the same DSSD pixel. The $\gamma $-rays from the decay of the isomer were detected using three Ge clover detectors placed around the DSSD. The inferred decay pattern of the isomer, based on the observed $\gamma $-rays, including two high-energy transitions observed in earlier prompt studies, indicate that the isomer decays to an excited two-quasiparticle or octupole vibrational band.\\ *Supp. by USDOE Grant DE-FG02-94ER40848 and W-31-109-ENG-38. [Preview Abstract] |
Tuesday, September 20, 2005 9:15PM - 9:30PM |
DG.00010: Shape trends and triaxiality in neutron-rich odd-mass Y and Nb isotopes Y.X. Luo, J.O. Rasmussen, I. Stefanescu, A. Gelberg, J.H. Hamilton, A.V. Ramayya, J.K. Hwang, S.J. Zhu, P.M. Gore, D. Fong, E.F. Jones, S.C. Wu, I.Y. Lee, T.N. Ginter, M.C. Ma, G.M. Ter-Akopian, A.V. Daniel, M.A. Stoyer, R. Donangelo New level schemes of $^{ 99,101}$Y (Z = 39) and $^{101,105}$Nb (Z = 41) are established from prompt $\gamma -\gamma -\gamma $ coincidences from the fission of $^{252}$Cf at Gammasphere. Bands of $\pi $5/2$^{+}$[422], $\pi $5/2$^{-}$[303] and $\pi $3/2$^{-}$[301] are extended to provide information on nuclear shapes in this odd-Z region. With the Tc (Z = 43), Rh (Z = 45) data and neighboring even-Z data, the Y and Nb isotopes are discussed in terms of shape transition and triaxiality. The pronounced difference observed in the signature splittings between Y and Tc, Rh isotopes indicates an axially-symmetric deformed shape in the Y isotopes, and, large and near maximum triaxiality in Tc-Rh isotopes. Triaxial-rotor-plus-particle model calculations strongly support a pure axially-symmetric shape with large quadrupole deformation in Y isotopes. The model calculations yielded $\gamma $ values from -19\r{ } to -13\r{ } for the 5/2$^{+}$ [422] ground-state bands of $^{101,103,105}$Nb and -5\r{ } for the two negative-parity bands in $^{101}$Nb. [Preview Abstract] |
Tuesday, September 20, 2005 9:30PM - 9:45PM |
DG.00011: In-beam $\gamma$-ray spectroscopy of a neutron-rich nucleus of $^{240}$U T. Ishii, M. Asai, M. Matsuda, S. Ichikawa, S. Shigematsu, J. Kaneko, T. Kohno, M. Ogawa, A. Makishima, I. Hossain We have measured deexcitation $\gamma$ rays in a neutron-rich nucleus of $^{240}$U for the first time. The $^{240}$U nuclei were produced by the two-neutron-transfer reaction of a 200-MeV $^{18}$O beam with a $^{238}$U target at the JAERI tandem booster facility. Outgoing nuclei and $\gamma$ rays were measured using 4 Si $\Delta E$-$E$ detectors and 7 Ge detectors, respectively, and $\Delta E$-$E$-$\gamma$-($\gamma$)-$t$ coincidence data were recorded. The outgoing nuclei were clearly separated not only by the atomic number but by the mass number on the $E$-$\Delta E$ plots. The $\gamma$ rays in $^{240}$U were identified by taking coincidence with $^{16}$O; the excitation energies of $^{240}$U were selected below the neutron separation energy by the kinetic energies of $^{16}$O. The multipolarities of $\gamma$-rays in $^{240}$U were determined by the in-plane to out-of-plane anisotropies of $\gamma$ rays. The ground-state band and the $K^{\pi}=0^{-}$ octupole band of $^{240}$U were established up to 12$^{+}$ and 9$^{-}$, respectively. The moment of inertia for the ground-state band of $^{240}$U is consistent with the systematics of $\beta_2$ and $\beta_4$ deformations in actinide nuclei. The octupole-band head of $^{240}$U is higher than those of $^{236,238}$U by about a hundred keV, suggesting that a secondary maximum of octupole correlations exists at $N=144-146$ in U isotopes. [Preview Abstract] |
Tuesday, September 20, 2005 9:45PM - 10:00PM |
DG.00012: Alpha-gamma decay studies of $^{261}$Rf and $^{257}$No M. Asai, K. Tsukada, T. Ishii, Y. Nagame, I. Nishinaka, K. Akiyama, A. Toyoshima, S. Ichikawa, T. Ichikawa, M. Sakama, H. Haba, K. Sueki, M. Shibata, Y. Kojima, Y. Oura Alpha-gamma and alpha-electron coincidence measurements were performed for the $\alpha$ decay of $^{261}$Rf and $^{257}$No to establish Nilsson single-particle states in odd-mass superheavy nuclei. The neutron single-particle configuration of 3/2[622] has been assigned to the ground state of $^{257}$No as well as to the 124.1 keV level in $^{253}$Fm. It was found that the ground state configuration of $^{257}$No is different from that of the lighter $N=155$ isotones $^{255}$Fm and $^{253}$Cf. Measured excitation energy in $^{257}$No populated by the $\alpha$ decay of $^{261}$Rf ($T_{1/2}=67$~s) revealed that another $\alpha$-decaying state in $^{261}$Rf with $T_{1/2}=4.2$~s reported in the $\alpha$-decay chain of $^{277}$112 is not the ground state but an isomeric state. The ground state configuration of $^{261}$Rf is discussed on the basis of the $\alpha$-$\gamma$ coincidence results. [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