Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session PE: Nuclear Structure A~100-120 |
Hide Abstracts |
Chair: Steven Pain, Oak Ridge National Laboratory Room: Sweeney Ballroom D |
Saturday, October 31, 2015 10:30AM - 10:42AM |
PE.00001: Photon strength function of $^{97}$Zr Shea Mosby, Aaron Couture, Hye Young Lee Some of the major questions in stockpile stewardship require nuclear reaction rates on fission fragments where there are few or no experimental constraints. Theoretical calculations are an alternative, but their reliability is ultimately limited by our incomplete understanding of such physics inputs as the photon strength function. $^{96}$Zr lies near the light mass peak for $^{239}$Pu fission, and neutron capture on and near this nucleus is of great importance for applications. The DANCE array at LANSCE and the Apollo array coupled to HELIOS at Argonne National Laboratory offer complementary probes into the neutron capture reaction, and an experimental campaign is underway to study $^{96}$Zr(n,$\gamma$) and $^{96}$Zr($d,p$) with these instruments. The status of these reaction studies will be presented. [Preview Abstract] |
Saturday, October 31, 2015 10:42AM - 10:54AM |
PE.00002: Deformed Structures and Shape Coexistence in Zr-98 Bruno Olaizola The nuclear structure of the zirconium isotopes evolves from a mid-open neutron shell deformed region ($^{80}$Zr), through a closed shell ($^{90}$Zr), to a closed subshell ($^{96}$Zr), and then to a sudden reappearance of deformation ($^{100}$Zr). This rapid onset of deformation across the Zr isotopes is unprecedented, and the issue of how collectivity appears and disappears in these isotopes is of special interest. Until recently, only $^{98}$Zr (and maybe $^{100}$Zr) had indirect and weak evidence for shape coexistence, with only speculative interpretation of the experiments. Recent results from high precision B(E2) measurements provided direct evidence of shape coexistence in $^{94}$Zr and suggested that it may happen in many other nuclei in this region. In order to provide direct evidence of shape coexistence in $^{98}$Zr a high-statistical-quality $\gamma\gamma$ experiment was carried out with the $8\pi$ spectrometer at ISAC-TRIUMF. The array consists of 20 Compton-suppressed hyper-pure germanium detectors plus $\beta$ particle and conversion electron detectors. Excited states up to $\sim5$ MeV in $^{98}$Zr were populated in the $\beta^-$ decay of $^{98}$Y J$^\pi=(0^-)$ and $^{98m}$Y J=(4,5). Preliminary results on key branching ratios will be presented. [Preview Abstract] |
Saturday, October 31, 2015 10:54AM - 11:06AM |
PE.00003: New analysis of levels in $^{96,100}$Y J.H. Hamilton, E.H. Wang, A. Lemasson, A.V. Ramayya, J.K. Hwang, A. Navin, M. Rejmund, S. Bhattacharyya, Y.X. Luo, J.O. Rasmussen, S.J. Zhu, G.M. Ter-Akopian, Yu.Ts. Oganessian Exited states of neutron rich $^{96,100}$Y have been studied by analyzing the high statistics $\gamma$-$\gamma$-$\gamma$ and $\gamma$-$\gamma$-$\gamma$-$\gamma$ coincidence data from the spontaneous fission of $^{252}$Cf at Gammasphere and also from the prompt $\gamma$-rays in coincidence with isotopically-identified fission fragments using VAMOS++ and EXOGAM at GANIL by using $^{238}$U beams on a $^{9}$Be target at energies around the Coulomb barrier. Nine new transitions and 6 new levels in $^{96}$Y, and 25 new transitions and 17 new levels in $^{100}$Y have been identified. Spins and parities are tentatively assigned according to the systematics. A small deformation with near spherical shape is proposed for $^{96}$Y. Bands in $^{100}$Y are proposed to be pairing free ones with very large deformation parameter ($\beta_2$=0.35(4) [1]). Two of the new bands in $^{100}$Y can form a 4$^+$ $\pi$5/2[422]+$\nu$3/2[411] and 5$^+$ $\pi$5/2[422]+$\nu$5/2[413] neutron pseudo spin doublet. The results are consistent with the onset of very strong deformation at N=59 among Y isotopes.\\[4pt] [1] J. Phys. G: Nucl. Part. Phys. {\bf 37}, 105103 (2010). [Preview Abstract] |
Saturday, October 31, 2015 11:06AM - 11:18AM |
PE.00004: Structure of positive parity bands and observation of magnetic rotation in $^{108}$Ag Jasmine Sethi, R. Palit The interplay of nuclear forces among the neutron particles (holes) and proton holes (particles) in the odd-odd nuclei gives rise to a variety of shapes and hence novel modes of excitations. The odd-odd nuclei in the A $\sim$ 110 region have proton holes in the g$_{9/2}$ orbital and the neutron particles in the h$_{11/2}$ orbitals. A systematic study of shears mechanism in A $\sim$ 110 region indicates the presence of magnetic rotation (MR) phenomenon in Ag and In isotopes. Therefore, the structure of doubly odd $^{108}$Ag nucleus was probed in two different reactions, i.e, $^{100}$Mo($^{11}$B, 4n)$^{108}$Ag at 39 MeV and $^{94}$Zr($^{18}$O, p3n)$^{108}$Ag at 72 MeV beam energies. The emitted $\gamma $-rays were detected using the Indian National Gamma Array (INGA) at TIFR, Mumbai. A significant number of new transitions and energy levels were identified [1]. Lifetime measurements, using the Doppler shift attenuation method, have been carried out for a positive parity dipole band. Tilted Axis Cranking (TAC) calculations have been performed for two positive parity dipole bands. \\[4pt] [1] J. Sethi, et al., Phys. Lett. B \textbf{725}, 85 (2013). [Preview Abstract] |
Saturday, October 31, 2015 11:18AM - 11:30AM |
PE.00005: Excited state lifetimes in 109Ru, 109Pd as a probe for structure in the neutron-rich A-100 region M.K. Smith, B. Bucher, A. Aprahamian, H. Mach, G. Simpson, J. Rissanen, J. Aysto, T. Eronen, D. Ghita, P. Karvonen, A. Jokinen, I.D. Moore, H. Penttila, M. Reponen, C. Weber, A. Saastomoinen, W. Kurcewicz, I.M. Fraile, B. Olaizola, E. Ruchowska The evolution of structure in neutron-rich nuclei can occur quite rapidly. In the A=110 region, the onset of deformation is not well-characterized, and signatures such as triaxial deformations, shape coexistence and oblate configurations have been reported within a small window of the nuclear landscape. We have investigated the A=109 $\beta$-decay chain from the fission of 238U at the Univ. of Jyvaskyla IGISOL facility. Level lifetimes and gamma-ray transitions were measured with a multi-detector array of 1 NE111A plastic, 2 HPGe, and 2 LaBr3 detectors. Events recorded in $\beta$-$\gamma$-$\gamma$ triple coincidence were used to construct/check level schemes and extract level lifetimes via the fast-timing method pioneered by H. Mach. Results will be presented on the low energy structure of 109Ru, in context to the A=109 decay chain including 109Tc and 109Pd. In each, new levels, transitions and lifetimes are measured for the first time [Preview Abstract] |
Saturday, October 31, 2015 11:30AM - 11:42AM |
PE.00006: Search for the heaviest N = Z alpha emitters Yongchi Xiao, Shintaro Go, Robert Grzywacz, Karolina Kolos, Katsuhisa Nishio, Riccardo Orlandi, Hiroyuki Makii, Kentaro Hirose, Ichiro Nishinaka, Hiroshi Ikezoe, James Smallcombe, Romain Leguillon, Krzysztof Rykaczewski, Nathan Brewer, Martin Veselsky, Carl Gross, Costel Petrache, Andrei Andreyev, David Jenkins, Bob Wadsworth, Mike Bentley, Chiara Mazzocchi, Fritz Peter Hessberger, Giacomo de Angelis, Luis Sarmiento The enhancement of alpha-decay probability for nuclei above $^{100}$Sn is expected because valence protons and neutrons above Z=N=50 occupy the same single-particle orbitals. The program to search for new alpha emitters in this region was initiated recently at the JAEA Tandem Laboratory at Tokai, Japan, where beams up to 30-50 pnA could be used. We performed proof-of-principle experiments with the Recoil Mass Separator (RMS) and digital electronics, which resulted in the observation of several $^{109}$Xe alpha decay chains. The first discovery-aimed experiment, which searched for the $^{113}$Ba alpha decay took place in December 2014, where possible candidates for the alpha decay of $^{113}$Ba were observed. The current status of analysis will be presented. [Preview Abstract] |
Saturday, October 31, 2015 11:42AM - 11:54AM |
PE.00007: Theoretical study of triaxial shapes of neutron-rich Mo and Ru nuclei Chunli Zhang, Gowhar Bhat, Witold Nazarewicz, Javid Sheikh, Yue Shi Recently, transition quadrupole moments in rotational bands of even-mass neutron-rich isotopes of molybdenum and ruthenium nuclei have been measured. To understand experimental data on rotational bands in the neutron-rich Mo-Ru region, we carried out theoretical analysis of moments of inertia, shapes, and transition quadrupole moments of neutron-rich even-even nuclei around $^{110}$Ru using self-consistent mean-field and shell model techniques. Our self-consistent DFT calculations predict triaxial ground-state deformations in $^{106,108}$Mo and $^{108.110,112}$Ru and reproduce the observed low-frequency behavior of moments of inertia. As the rotational frequency increases, a negative-$\gamma$ structure becomes energetically favored. The computed transition quadrupole moments vary with angular momentum, which reflects deformation changes with rotation; those variations are consistent with experiment. The TPSM calculations explain the observed band structures assuming stable triaxial shapes. [Preview Abstract] |
Saturday, October 31, 2015 11:54AM - 12:06PM |
PE.00008: Magnetic Moments of the 2$^+_1$ and 4$^+_1$ States in $^{110}$SN Gerfried Kumbartzki, N. Benczer-Koller, L. Bernstein, D.A. Torres, K.-H. Speidel, J.M. Allmond, P. Fallon, I. Abramovic, J.M. Bevins, A. Hurst, Z.E. Guevara, G. G\"{u}rdal, L. Kirsch, T. LaPlace, A. Lo, H.L. Crawford, E. Matthew, I. Meyers, L. Phair, F. Ramirez, Y.Y. Sharon, A. Wiens The structure of the Sn isotopes has been studied via measurements of B(E2;2$^+_1 \rightarrow 0^+_1$) transition rates and $g$ factors of 2$^+_1$ states. Values of B(E2)'s in the lighter isotopes show an increase in collectivity below midshell, contrary to predictions from shell model calculations. In order to better establish the structure of these neutron-deficient isotopes, measurements of $g$ factors in $^{110}$Sn, where the neutrons might occupy both the $g_{7/2}$ and $d_{5/2}$ orbitals, have been carried out. The states of interest were populated in the reaction $^{12}$C($^{106}$Cd, 2$\alpha$)$^{110}$Sn, at the LBNL 88 inch cyclotron. The $\gamma$ rays were detected in ORNL and LBNL clover detectors. The transient field technique was used to obtain magnetic moments. The details of the experiment and the results will be presented. [Preview Abstract] |
Saturday, October 31, 2015 12:06PM - 12:18PM |
PE.00009: Study of Multiphonon $\gamma\gamma$-Band Through Modified Soft Rotor Formula Parveen Kumari, Harish Mohan Mittal The structure of multiphonon $\gamma\gamma$-band of $^{156}Gd$ is investigated by using the Modified Soft Rotor Formula (MSRF). The Modified Soft Rotor Formula proposed by Gupta et al. [1] is given as: \begin{equation} E(I)=EK + \frac{\hbar^{2} I(I+1)}{2\theta(1+ \sigma I)}, \end{equation} where $\theta$ is moment of inertia, $\sigma$ is known as softness parameter and $EK$ is constant energy term. The calculated values of moment of inertia of $\gamma\gamma$-band are almost equal to the moment of inertia of $\gamma$-band. The study of K=2 $\gamma$-band and K=4 $\gamma\gamma$-band using MSRF yield good energy values. The small values of the softness parameter and positive values of moment of inertia are obtained for multiphonon band. The staggering pattern in $\gamma$-band and $\gamma\gamma$-band are also studied. Recently, the study of multiphoon $\gamma\gamma$-band in $^{112}Ru$ and isotopes of $Mo$ have been done by Kumari and Mittal [2]. \\[4pt] [1] J. B. Gupta, S. Sharma and V. Katoch, Pramana J. of Phys., 81, 75 (2013).\\[0pt] [2] Parveen Kumari and H.M. Mittal, Physica Scripta (2015) In Press. [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