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 CE: Mini-symposium on Nuclear Moments II |
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Sponsoring Units: DNP JPS Chair: Paul Mantica, Michigan State University Room: Ritz-Carlton Hotel Amphitheatre |
Tuesday, September 20, 2005 2:00PM - 2:30PM |
CE.00001: Towards better understanding of the Recoil-In-Vacuum technique: hyperfine interactions and their variation with element and ion charge state for application to g-factor measurements in ps lifetime nuclear levels. Invited Speaker: The recoil-in-vacuum [RIV] method for excited state nuclear g-factor measurements in the ps lifetime range has been shown recently to offer attractive possibilities for application with RIBs combined with modern detector arrays. In the recent work, as in all prior RIV studies, the magnetic hyperfine fields acting at the nuclei of the recoiling ions have been treated empirically, calibrated using states of known lifetime and g-factor. It is now a matter of clear importance to establish how these fields vary with element and ionization state [dependent on beam energy and target thickness] in order to discover how the RIV approach may be best utilized. The ability to calculate lifetimes and hyperfine interaction strengths in complex electronic levels has advanced markedly with modern computation techniques. Physics ideas contributing to the selection of the electronic states of importance will be discussed and first evidence for the value of a-priori calculations presented. In collaboration with Jirina Rikovska Stone, Oxford University and the University of Maryland; Charlotte Froese Fischer, Vanderbilt University. [Preview Abstract] |
Tuesday, September 20, 2005 2:30PM - 2:45PM |
CE.00002: Monte-Carlo Shell Model calculations of Xe, Ba isotopes Noritaka Shimizu, Takaharu Otsuka, Takahiro Mizusaki, Michio Honma We discuss the low-lying quadrupole collective states of Xe, Ba isotopes around $A=134$ microscopically based on the Monte-Carlo shell model (MCSM). The MCSM enables us to apply the nuclear-shell-model calculation to the study of medium-heavy nuclei. The magnetic moments and several other values of these isotopes provided by the MCSM reproduce experimental values well, and show some features of gradual transition between spherical vibrator and triaxial deformation. [Preview Abstract] |
Tuesday, September 20, 2005 2:45PM - 3:00PM |
CE.00003: Magnetic moment of a mixed-symmetry state of Zr nuclei V. Werner, N. Pietralla, N. Benczer-Koller, G. Kumbartzki, E. Stefanova, C. Fransen, P. von Brentano, H. Ai, R.F. Casten, A. Heinz, E.A. McCutchan, D.A. Meyer, J. Qian, E. Williams, R. Winkler, R.B. Cakirli, C.R. Fitzpatrick, G. G\"urdal Mixed-symmetric states are quadrupole collective states with anti-symmetric parts in their pn wave function. Breaking of the proton-neutron (pn) symmetry was discussed for $^{92}$Zr within the IBM-2, the shell model (SM), and the quasiparticle phonon model (QPM). The models differ in quantifying the pn symmetry breaking, which leads to substantial differences in the predictions for the g factor of the one-phonon $2^+_{1, {\rm ms}}$ state with predominantly mixed-symmetry character. The g factor of this state is difficult to measure due to its short lifetime. First measurements in Zr isotopes have been performed at WNSL using the transient field technique. Results will be compared to model predictions. Work supported by USDOE grants DE-FG02-91ER-40609, DE-FG52-05NA25929, and DE-FG02-88ER40417, U.S. NSF (RU and SB), and DFG under Br 799/12-1. [Preview Abstract] |
Tuesday, September 20, 2005 3:00PM - 3:15PM |
CE.00004: Nuclear g-factor measurements for the 2$_{1}^{+}$ states of radioactive Te isotopes by the recoil-in-vacuum technique C.R. Bingham, M. Danchev, N.J. Stone, J.R. Stone, C.L. Timlin, A.E. Stuchbery, C. Baktash, J. Beene, A. Galindo-Uribarri, C.J. Gross, J. Pavan, D.C. Radford, N. Benczer-Koller, G. Kumbartzki, J. Dupak, C. Barton, N.V. Zamfir Coulomb excitation of the first excited state of radioactive ion beams has been carried out at HRIBF by scattering the RIBs from C foils and observing the recoiling C ions and de-excitation gamma rays of the RIB.\footnote{See e.g., D. C. Radford, et al., Phys. Rev. Lett. 88, 222501 (2002).\par } This method also yields an angular correlation of the emitted gamma ray with respect to the direction of C recoil. In Coulomb excitation the nuclear spin is initially oriented by the reaction, yielding strong angular correlation of the emitted gamma ray with respect to the direction of C recoil. As the RIB recoils into the vacuum downstream from the thin target, the angular correlation is attenuated due to de-orientation of the spin resulting from its precession about the total angular momentum of the ion. The attenuation of the angular correlation depends on g$^{2}$ and the mean life of the state. The experimental results for $^{132}$Te will be presented and the g-factors of $^{132,134,136}$Te will be discussed. [Preview Abstract] |
Tuesday, September 20, 2005 3:15PM - 3:30PM |
CE.00005: Short-lived excited-state $g$ factors of fast $^{38,40}$S fragments. A.D. Davies, A.E. Stuchbery, A. Becerril, C.M. Campbell, J.M. Cook, D.C. Dinca, A. Gade, S.N. Liddick, P.F. Mantica, W.F. Mueller, H. Olliver, J.R. Terry, B.E. Tomlin, K. Yoneda, P.M. Davidson, A.N. Wilson The transient field technique for measuring short-lived excited-state magnetic dipole moments generally requires ion velocities comparable to $Zv_{0}$ ($v_{0}=c/137$) or lower, which, at face value, would preclude the study of the wide range of isotopes available at fragmentation facilities. However, stringent testing of nuclear models far from stability can be realized with $g$-factor measurements on these isotopes, once the experimental challenges are overcome. Measurements performed at the NSCL's Coupled Cyclotron Facility have extended the transient field technique to radionuclides produced as in-flight fast fragments. The high velocity transient field technique was applied to intermediate-energy beams of $^{38}$S and $^{40}$S. The signs of their first-excited $2^{+}$ state $g$ factors were obtained, and with a parametrization of the transient field strength at high velocities, the $g$-factor magnitudes were extracted. Results, experimental details, and future outlook will be presented. [Preview Abstract] |
Tuesday, September 20, 2005 3:30PM - 3:45PM |
CE.00006: Doppler-broadened lineshapes from Coulomb-excita\-tion of fast fragment beams: implications for $g$-factor and lifetime measurements Andrew Stuchbery, Andrew Davies Doppler-broadened lineshapes were observed in a recent measurement of the $g$ factor of the first 2$^{+}$ state in $^{38}$S (see the contribution of A.D. Davies \textit{et al}.). Beams of the neutron-rich isotope were produced by fragmentation and delivered at 40 MeV/nucleon onto a target consisting of Au and Fe layers, 355 mg/cm$^{2}$ and 110 mg/cm$^{2}$ thick, respectively. The beam ions were Coulomb excited and subjected to the transient field during transit through the Fe layer. Since the transit time through the target layers is of the order of the lifetime of the 2$^{+}$ state (5 ps), about half of the nuclei decay whilst slowing in the target. The gamma-ray spectra therefore show Doppler-broadened lines. A computer code has been developed to interpret and analyze these lineshapes. The implications for the $g$-factor measurement and the potential for future applications to lifetime measurements will be discussed. [Preview Abstract] |
Tuesday, September 20, 2005 3:45PM - 4:00PM |
CE.00007: New developments for the measurements of magnetic moments of sub-ps states using RIB-projectile excitation and transfer reactions Gerfried Kumbartzki, Noemie Benczer-Koller It is instrinsically difficult to measure nuclear moments reliably and with sufficient accuracy especially for short-lived excited states of rare isotopes. The application of projectile excitation using transient hyperfine fields for the magnetic interaction is an established method. The latest developments of the technique and results for stable and radioactive projectiles will be discussed. In addition to the Coulomb excitation of the projectiles on carbon targets, the transfer of an alpha particle to the projectile leads to probe ions, some radioactive, which are otherwise not accessible as beams, thus extending the reach of the method. [Preview Abstract] |
Tuesday, September 20, 2005 4:00PM - 4:15PM |
CE.00008: Study of neutron rich nuclei by CYRIC new cyclotron Tsutomu Shinozuka, Masahiro Fujita, Akiyoshi Yamazaki, Mifuyu Ukai, Tomokazu Suzuki, Yuji Miyashita, Nozomi Sato, Mitsuharu Ohguma, Hirokazu Tamura, Takeshi Koike, Yusuke Miura, Sari Kinoshita, Yue Ma, Kotaro Shirotori The AVF cyclotron at CYRIC has been replaced from K=50 MeV AVF cyclotron to K=130 MeV AVF cyclotron, which accelerates heavy ions up to Ar with ECR ion source and high intensity protons with negative Hydrogen ion source. All of the missions for replacement is almost completed. The several experiments for nuclear spectroscopy of unstable nuclei with the new cyclotron has been planned and partly advanced. \begin {itemize} \item Development of RF Ion Guide Isotope Separator toward to 78Ni \item Moment measurements with 6 clover detectors by $\gamma- \gamma $ angular correlation for low excited states of neutron rich nuclei. \item In-beam gamma ray measurements with 6 clovers and 14 single Ge detectors (Hyperball 2) \end{itemize} The details of developments and several experimental results will be presented. [Preview Abstract] |
Tuesday, September 20, 2005 4:15PM - 4:30PM |
CE.00009: Nuclear Moments of the Neutron-Deficient Lanthanum Isotopes by Collinear Laser Spectroscopy H. Iimura, M. Koizumi, M. Miyabe, M. Oba, T. Shibata, N. Shinohara, Y. Ishida, T. Horiguchi, H.A. Schuessler The hyperfine-structure-splitting constants and isotope shifts of the 6s$^{2}$ $^{1}$S$_{0}$-5d6p $^{3}$D$_{1}$ ($\lambda$=538 nm) and 5d$^{2}$ $^{3}$P$_{2}$-5d6p $^{1}$D$_{2}$ ($\lambda$=548 nm) transitions of singly charged lanthanum ion have been measured by collinear laser-ion-beam spectroscopy for the neutron-deficient isotopes $^{135}$La, $^{137}$La, and $^{138}$La. The magnetic moments and quadrupole moments of the ground states of these isotopes have been determined from the measurements. The ratio of the magnetic dipole coupling constants A(138)/A(139) of the level 5d6p $^{3}$D$_{1}$ has shown a -0.35(23)$\%$ hyperfine anomaly with respect to the NMR ratio of the nuclear g factors. These moments and the changes in the mean-square nuclear charge radii determined from the isotope shifts are compared with theoretical predictions. Work to measure more neutron-deficient lanthanum isotopes is in progress by our laser spectroscopy collaboration at the ISAC facility at TRIUMF. [Preview Abstract] |
Tuesday, September 20, 2005 4:30PM - 4:45PM |
CE.00010: New laser spectroscopic method for the measurement of nuclear moments. Takeshi Furukawa, Yukari Matsuo, Atsushi Hatakeyama, Yoshimitsu Fukuyama, Tohru Kobayashi, Hideaki Izumi, Tadashi Shimoda We propose here a versatile method to measure the nuclear moments of unstable nuclei through laser spectroscopic detection of atoms trapped in superfluid helium (He II). This method takes advantage of the optical pumping of atoms in He II and the ``laser-microwave double resonance method.'' It enables us to determine the moments, hitherto difficult to be measured by other methods, of unstable nuclei far from the stability line. For the development of this method, we have been studying optical pumping of impurity atoms in He II. The electronic spin relaxation time of the atoms in He II is the key quantity for the success of optical pumping, but no result of the measurement has been reported so far. We have measured the spin relaxation time $T_{1}$ of Cs atoms in He II. This success is due to special care to cope with a serious decrease in the number of Cs atoms in the observation region caused by the large convection in introducing the atoms with laser sputtering technique. The measured relaxation time of $T_{1}$=2.24(19) s is extraordinary long, which encourages us to take advantage of He II as a suitable environment for trapping unstable nuclei and for performing laser spectroscopy for the measurement of nuclear moments. [Preview Abstract] |
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