Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session KL: Nuclear Structure V |
Hide Abstracts |
Chair: Michio Honma, University of Aizu Room: Queens 6 |
Saturday, October 17, 2009 9:00AM - 9:15AM |
KL.00001: Collective behavior in $^{71}$As R.A. Kaye, C.J. Drover, S.R. Arora, N.R. Baker, S.L. Tabor, T.A. Hinners, C.R. Hoffman, S. Lee, J. D\"{o}ring, J.K. Bruckman High-spin states in $^{71}$As were studied using the $^{54}$Fe($^{23}$Na, $\alpha$2$p$) reaction at 80 MeV provided by the John D. Fox superconducting accelerator at Florida State University. Prompt $\gamma$-$\gamma$ coincidences were measured using an array of 10 Compton-suppressed Ge detectors. The yrast band based on the $\pi$$g_{9/2}$ intrinsic configuration was extended up to a $(\frac{37}{2}^+)$ state and now shows evidence of a band crossing near $\hbar \omega = 0.7$ MeV. Lifetimes of 17 excited states were measured using the Doppler-shift attenuation method applied to the experimental line shapes of decays in three known rotational bands. Transition quadrupole moments $Q_t$ inferred from the lifetimes indicate that moderate to high collective behavior persists to the highest observed spins in the lowest positive- and negative-parity bands. The band suggested to be based on the $\pi$$f_{7/2}$ orbital shows similar collectivity and large intraband $B(M1)$ strengths, but the associated $Q_t$ values are somewhat smaller than expected from cranked Woods-Saxon calculations. These results will also be compared with the predictions of the projected shell model. [Preview Abstract] |
Saturday, October 17, 2009 9:15AM - 9:30AM |
KL.00002: Shape Coexistence in $^{72}$Se C.J. Lister, S.M. Fischer, E.A. McCutchan, T. Ahn, R.J. Casperson, A. Heinz, G. Ilie, J. Qian, E. Williams, R. Winkler One of the original candidates for shape co-existence in nuclei was $^{72}$Se [1,2]. We have collected extensive new data, both ``in-beam'' following the $^{40}$Ca($^{36}$Ar,4p)$^{72}$Se reaction using Gammasphere at Argonne's ATLAS accelerator, and from the decay of $^{72}$Br populated in the $^{58}$Ni($^{16}$O,pn) reaction studied at WNSL Yale. A new J$^{\pi }$=0$^{+}$ state was found at 1876 keV, the published [2] decay scheme was corrected, and twenty-six new levels were established. This detailed spectroscopy of low-lying states helps to delineate the two shape minima. The mixing of prolate-deformed and near-spherical states can be now quantified, and the gamma decay path from high-spin can be followed. The inferred groundstate shape is consistent with trends in experiment and calculation of the selenium isotopes [3,4]. \\[4pt] [1] J.H. Hamilton, \textit{et al.,} Phys. Rev. Letts. 32 239 (1974)\\[0pt] [2] W.E. Collins, \textit{et al., }Phys.Rev. C9, 1457 (1974)\\[0pt] [3] S.M. Fischer, \textit{et al.,} Phys.Rev.Lett. 84, 4064 (2000)\\[0pt] [4] J. Ljungvall, \textit{et al., }Phys.Rev.Lett. 100, 102502 (2008) [Preview Abstract] |
Saturday, October 17, 2009 9:30AM - 9:45AM |
KL.00003: Photon scattering on the $0\nu2\beta$-decay daughter nucleus candidate $^{76}$Se N.M. Cooper, V. Werner, L. Bettermann, F. Reichelt, N. Pietralla, D. Savran, K. Sonnabend, M. Fritzsche, S.W. Yates The Pygmy dipole resonance (PDR) was extensively studied in spherical nuclei, especially along the N=82 shell closure. The PDR is thought to be a dipole vibration of an inert proton-neutron core against a neutron skin. The dependence of the PDR on deformation has so far not been tested in nuclei with small N/Z ratios. The dipole strength distribution up to 9 MeV may serve as a test for QRPA calculations relevant to $0\nu2\beta$-decay. Photon scattering experiments on $^{76}$Se have been performed using incident photons from the S-DALINAC facility at the TU-Darmstadt. The isotopically enriched sample was irradiated at different photon endpoint energies. Preliminary results will be presented. [Preview Abstract] |
Saturday, October 17, 2009 9:45AM - 10:00AM |
KL.00004: Generator coordinate method analysis of low-lying and high-spin states in medium- and heavy-mass nuclei Koji Higashiyama, Naotaka Yoshinaga The generator coordinate method (GCM) is applied to the neutron-rich Se, and Ge isotopes, where the monopole and quadrupole pairing plus quadrupole-quadrupole interaction is employed as an effective interaction. As for single-particle levels, all the relevant orbitals, 0$g_{9/2}$, 1$p_{1/2}$, 1$p_{3/2}$, 0$f_{5/2}$, in the major shell between the magic numbers 28 and 50 are taken into account for both neutrons and protons. The energy spectra and electromagnetic transitions obtained by the GCM are compared to the shell model results and the experimental data. The model reproduces well the energy levels of high-spin states as well as the low-lying states. The structure of the high-spin states and low-lying collective states is analyzed through the GCM wave functions. It is shown that the triaxial components play essential roles in describing the quasi-\textit{$\gamma $} bands. [Preview Abstract] |
Saturday, October 17, 2009 10:00AM - 10:15AM |
KL.00005: High-spin states of $^{70}$Ge and a role of g$_{9/2}$ orbit Masahiko Sugawara, Yosuke Toh, Masumi Oshima, Mitsuo Koizumi, Atsushi Kimura, Akihiko Osa, Yuichi Hatsukawa, Hideshige Kusakari, Jun Goto, Michio Honma, Munetake Hasegawa, Kazunari Kaneko High-spin states of $^{70}$Ge have been studied via the $^{60}$Ni($^{12}$C, 2$p \gamma$)$^{70}$Ge reaction at 45 MeV. The ground-state band and the second 0$^{+}$ band have been extended to the 12$^{+}$ and 8$^{+}$ states, respectively. Two negative-parity bands, one of which has a coupled strucure and the other has a decoupled structure, have been observed. Although the decoupled one was known previously up to the (21-) state, the order of $E$2 transitons up to the 15$^{-}$ state have been largely modified by this experiment. The particle alignment observed in the ground-state band has been compared with those for the neighboring even Ge isotopes. The experimental level scheme has been compared with the shell model calculations in the model space ($2p_{3/2}$, $1f_{5/2}$, $2p_{1/2}$,$1g_{9/2}$) employing the two kinds of effective interactions, one of which is an extended $P+QQ$ and the other is developed from a renormalized G-matrix. [Preview Abstract] |
Saturday, October 17, 2009 10:15AM - 10:30AM |
KL.00006: Structure of $^{74-76}$Cu and $^{71-73}$Ni from $\beta$-decay studies Mustafa Rajabali, R. Grzywacz, S.N. Liddick, C. Mazzocchi, C. Bingham, I. Darby, J. Batchelder, K. Rykaczewski, P. Mantica, T. Baumann, T. Ginter, M. Pfutzner, K. Miernik, W. Krolas, S.V. Ilyushkin, J. Winger The low-energy excited states in $^{74-76}$Cu and $^{71-73}$Ni were populated through the beta decay of $^{74-76}$Ni and $^{71- 73}$Co isotopes respectively. The experiment was performed at the NSCL at MSU. The parent isotopes were obtained from the fragmentation of $^{86}$Kr beam, at 140 AMev, on a Be target. The experimental setup consisted primarily of a thick Double- sided Silicon Strip Detector for the correlation of implanted ions with their subsequent beta decays and the NSCL Segmented Germanium Array (SeGA) to monitor the emitted gamma rays. All detectors were read out with a new digital data acquisition system. Results from this experiment are interpreted using shell model with residual interactions which takes into account the monopole migration of single particle proton levels near $^{78} $Ni. Expected strong hindrance of M1 transitions was observed in $^{71-73}$Ni. The observed decay of $^{76}$Ni gives a first insight into the possible decay pattern of $^{78}$Ni. [Preview Abstract] |
Saturday, October 17, 2009 10:30AM - 10:45AM |
KL.00007: Beta decay studies of isobarically separated $^{81}$Zn Stephen Padgett, J.C. Batchelder, L. Cartegni, I.G. Darby, C.J. Gross, R. Grzywacz, S. Ilyushkin, S.N. Liddick, M. Madurga, T. Mendez, C. Mazzocchi, M. Rajabali, K.P. Rykaczewski, D. Shapira, J.A. Winger, E.F. Zganjar A new Low-energy Radioactive Ion Beam Spectroscopy Station (LeRIBSS) dedicated to the beta decay studies of $^{238}$U proton-induced fission products was constructed at the HRIBF at ORNL. The precision tuning of the high resolution magnetic separator allowed for almost complete suppression of the gallium ions produced at the rate of $10^6$ pps, thus enabling clean spectroscopy of samples of $^{81}$Zn produced at the rate of 30 pps. The beta decay of $^{81}$Zn populated states in the N=50 isotone, $^{81}$Ga, just three protons above $^{78}$Ni. This nucleus is an an important case to test the competition between allowed and forbidden beta decay transitions, which is essential to reliably predict beta decay lifetimes. [Preview Abstract] |
Saturday, October 17, 2009 10:45AM - 11:00AM |
KL.00008: Inverse kinematics RDDS lifetime measurements: $^{82}$Se E.T. Holland, V. Werner, J.R. Terry, R. Winkler, R.J. Casperson, A. Heinz, J. Qian, E. Williams, P.H. Regan, E.A. McCutchan, B. Shoraka, R. L\"uttke, C.W. Beausang, J.M. Allmond, D.A. Meyer, J. LeBlanc A new method for inverse kinematics lifetime measurements was introduced at WNSL. A heavy beam is Coulomb excited on a light target and subsequently stopped in a second foil, chosen so the forward scattered light nuclei can trespass the stopper and be detected by a Si detector. A particle-gamma coincidence requirement minimizes background, and fixes the quantization axis. Lifetimes are determined independent from the Coulomb excitation mechanism, and the measurement of attenuated angular distributions shall be used in future g factor measurements. $^{82}$Se is situated two neutrons below the N=50 shell closure. This allows to study the interplay between collective and single-particle degrees of freedom. We used a $^{82}$Se beam incident on a C target for lifetime measurements of high-lying excited states at a beam energy $\sim$25\% above the Coulomb barrier. The new RDDS method will be introduced, and first results on $^{82}$Se will be presented. [Preview Abstract] |
Saturday, October 17, 2009 11:00AM - 11:15AM |
KL.00009: Measurements of the $g$ factors of the low-lying excited states in stable even-even Ge nuclei G. G\"{u}rdal, G. Kumbartzki, N. Benczer-Koller, S.J.Q. Robinson, Y.Y. Sharon, L. Zamick, Z. Berant, T. Ahn, R. Casperson, R. Chevrier, A. Heinz, G. Henning, G. Ilie, D. McCarthey, J. Qian, A. Schmidt, J.R. Terry, W. Verner, E. Williams, R. Winkler The $g$ factors of the low-lying excited states of $^{72,74,76}$Ge were measured using the Transient Field (TF) technique, and the results will be presented. The states of interest were populated by projectile Coulomb excitation in inverse kinematics. The Ge nuclei were accelerated at the Yale ESTU Tandem Van de Graaff accelerator and impinged on C or Mg/gadolinium/copper targets. The measured $g$ factor results will be compared to the predictions of large-scale shell model calculations in the $p_{3/2}f_{5/2}p_{1/2}g_{9/2}$ space for both protons and neutrons. A summary of the $g$ factors of $2^+_1$, $4^+_1$ and $2^+_2$ states in the mass A $\sim$ 70 region will also be presented. [Preview Abstract] |
Saturday, October 17, 2009 11:15AM - 11:30AM |
KL.00010: Nuclear g-factor measurement for the low-lying state in $^{109}$Rh using On-line TDPAC technique and RF-IGISOL technique Yuji Miyashita, Hiroyuki Ouchi, Sayaka Izumi, Ayako Sasaki, Nozomi Sato, Miki Tateoka, Sayo Hoshino, Tetsuya Nagano, Wataru Yamashita, Akiyoshi Yamazaki, Kenzi Shimada, Takashi Ishida, Takashi Wakui, Tsutomu Shinozuka, Minoru Tanigaki To extend the studies on neutron-rich nuclei, we have developed an RF-IGISOL technique, which is combination of the gas catcher technique and the electrical field guiding technique with a large volume gas cell. As the first step to such approach, we are planning and trying the systematic measurement of g-factor in the neutron rich nuclei extracted as an radioactive beam from our RF-IGISOL at Tohoku University. The g-factor measurement for the low-lying state of $^{109}$Rh ($E_{x}$~=~225.98~keV, $T_{1/2}$~=~1.66~$\mu$s) is the first on-line experiment with our RF-IGISOL system. The g-factor for this state has been determined to be $g~=~$0.78~$^{+0.17}_{-0.03}$~$\mu_{N}$ by the on-line TDPAC method. In this contribution, the details of experimental results will be reported. [Preview Abstract] |
Saturday, October 17, 2009 11:30AM - 11:45AM |
KL.00011: Measurements of the magnetic moments of the excited $2_1^+$, $4^+_1$ and $2_2^+$ states in $^{106}$Pd G. Kumbartzki, G. G\"{u}rdal, N. Benczer-Koller, S.J.Q. Robinson, Y.Y. Sharon, L. Zamick, Z. Berant, T. Ahn, R. Casperson, A. Heinz, G. Ilie, D. McCarthey, J. Qian, A. Schmidt, J.R. Terry, E. Williams, R. Winkler The magnetic moments of the low-lying excited states of $^{106}$Pd were measured using the Transient Field (TF) technique, in order to compare the results with predictions from either collective model or shell model calculations. The states of interest were populated by projectile Coulomb excitation in inverse kinematics. The $^{106}$Pd beam was accelerated at the Yale ESTU Tandem Van de Graaff accelerator and impinged on a multilayer C/gadolinium/copper target. The measured magnetic moment of the excited $2_1^+$ state in $^{106}$Pd was compared to the results of previous measurements in the literature and of magnetic moment measurements in the neighboring Ru and Mo nuclei as a test of the Rutgers parametrization of the transient field in this region. [Preview Abstract] |
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