Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session DF: Nuclear Structure : Heavy Nuclei I |
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Chair: Walter Reviol, ANL Room: Berkeley & Clarendon |
Tuesday, October 12, 2021 9:30AM - 9:42AM |
DF.00001: Characterization of an experimental setup for two-proton transfer reaction measurements on gaseous targets Timothy V Daniels, Joanna Wuko, William T Jarratt, Calvin R Howell, James A Runge, Phillip S Barbeau, Albert Young, TIMOTHY C BLACK Disagreement between theoretical nuclear matrix element calculations complicates the possible measurement of the unknown neutrino mass scale through observation of neutrinoless double-beta decay. These calculations each make simplifying assumptions, and in particular the Quasi-Random Phase Approximation (QRPA) technique generally proceeds from a description of the ground states of the relevant nuclei as condensates of 0+ nucleon pairs, in analogy to the BCS theory of superconductivity. This can be tested by two-nucleon transfer reactions, which should then proceed mostly to the ground state of the residual nucleus. The (3He,n) reaction has been carried out at a dedicated time-of-flight system at TUNL on several nuclei of interest to double-beta decay, including 134Xe. The latter measurements were carried out with a gas cell target, and preliminary results from benchmark measurements carried out with 40Ar and 136Xe will be shown and compared with previous measurements. System performance, including timing resolution and background rates, will be discussed. |
Tuesday, October 12, 2021 9:42AM - 9:54AM |
DF.00002: Emerging Nuclear Collectivity: Coulomb Excitation of 106Cd Timothy Gray, James Allmond, Robert V Janssens, Wolfram Korten, David C Radford, Akaa D Ayangeakaa, Jon C Batchelder, Cornelius Beausang, Brian M Bucher, Matthew Q Buckner, Christopher M Campbell, Michael P Carpenter, Douglas Cline, Heather L Crawford, H David, Daniel Doherty, Paul Fallon, Alfredo Galindo-Uribarri, Andreas Gorgen, Carl J Gross, Katarzyna Hadynska-Klek, Malin Klintefjord, Kay Kolos, M Komorowska, Filip G Kondev, Gregory J Lane, Torben Lauritsen, Augusto O Macchiavelli, Pavel Napiorkowsi, Elizabeth Padilla-Rodal, L Prochniak, Walter Reviol, Demetrios G Sarantites, Julian Srebrny, Andrew E Stuchbery, Robert L Varner, Alexander J Wiens, Ching-Yen Wu, Chang-Hong Yu, John L Wood, K Wrzosek-Lipska, Shaofei Zhu, Magda Zielinska, Simone Bottoni, Steven D Pain, Michael T Febbraro Nuclear collectivity has traditionally been thought to evolve through stages of seniority, vibrational, and rotational character as one moves from closed to open-shell regions of the nuclear chart. While there are several robust examples of seniority and rotational character, isolating vibrational character has been more difficult, particularly due to the transitional nature between the extremes. The Cd isotopes (Z=48) were long thought of as textbook examples of vibrational nuclei where the low-lying excitation patterns are consistent with such an interpretation. However, this narrative has since been challenged with the ever growing body of nucleon-transfer and electromagnetic matrix element data, showing major discrepancies with the vibrational model. Alternative views now include everything from weakly deformed anharmonic vibrations with double shape coexistence to weakly deformed triaxial rotations with multi shape coexistence. Results from multi-step Coulomb excitation data of 106Cd on 208Pb will be presented and compared to recent interpretations and measurements, including anomalous DSAM-based lifetime values. Excitation of the low-lying states, including two excited 0+ states, was observed in the present study. We report the first measurement of B(E2; 2_1+ -> 0_2+) and B(E2; 2_1+ -> 0_3+), a crucial piece of data for determining the nature of the weak collectivity exhibited in the Cd isotopes. In addition, electric quadrupole moments will be presented for several of the low-lying states. The E2 matrix elements allow the Kumar-Cline sum rules to be applied, giving a model independent measure of deformation on a state-by-state basis. The experiment was performed at the ATLAS facility of Argonne National Laboratory using GRETINA-CHICO2. |
Tuesday, October 12, 2021 9:54AM - 10:06AM |
DF.00003: Modernization and Expansion of the Evaluated Nuclear Structure Data File Database (ENSDF) Adam Hayes, Elizabeth McCutchan, Shinjae Yoo, Cassandra Billings, Andrea Mattera, Donnie Mason, Sean McCorkle, Chris Morse, Shu Shu, Alejandro A Sonzogni, Carlos Soto, Shaofei Zhu, Filip G Kondev, Caleb Mattoon The Evaluated Nuclear Structure Data File (ENSDF) database is the comprehensive nuclear structure and decay database, containing all published experimental nuclear structure and decay data for the 3300 observed nuclides, along with carefully evaluated recommended values and uncertainties. ENSDF is the leading source of nuclear structure and decay data worldwide for both basic and applied sciences, exceeding 3.2M lookups per year via the NNDC website. A complete modernization of the ENSDF database is underway, transforming the restrictive 80-column ASCII format in use since its inception into an expansible Object-Oriented Database and API. The upgrade will allow for the addition of a wide variety of content (such as continuous spectra), efficiently deliver complex search results, and provide access to modern computational tools through a Python API. Machine learning techniques are being developed in parallel to automate the insertion of new results into the companion database for pre-evaluated published results (XUNDL), reducing the time between ENSDF evaluations and improving database currency. The modernized database will be amenable to the addition of arbitrary types of open data. |
Tuesday, October 12, 2021 10:06AM - 10:18AM |
DF.00004: Structure and shape of 126, 128Xe studied in Coulomb excitation measurements Stanimir P Kisyov, Ching-Yen Wu, Jack Henderson, JANUS collaboration The electromagnetic properties of 126, 128Xe were studied in Coulomb excitation measurements, performed at the National Superconducting Cyclotron Laboratory, MSU. 126, 128Xe nuclei were accelerated to 3.74 MeV/u and 3.81 MeV/u, respectively, and impinged on 196Pt and 208Pb targets resulting in low-energy Coulomb excitation. Emitted gamma-rays and scattered nuclei were detected using the SeGA-JANUS setup. Transition and diagonal matrix elements were extracted from the data using the GOSIA code1. The results for transition matrix elements are in agreement with previously measured values. Diagonal matrix elements for several excited states were newly determined and quadrupole moments were deduced. Preliminary results will be presented and compared to calculations within different theoretical models. |
Tuesday, October 12, 2021 10:18AM - 10:30AM |
DF.00005: Octupole vibrations and Coriolis-induced mixing in 244Pu, 246Cm and 248,250Cf Y. Qiu, S.S. Hota, C.J. Lister, T.L. Khoo, R.V.F. Janssens, I. Ahmad, M.P. Carpenter, J.P. Greene, F.G. Kondev, T. Lauritsen, D. Seweryniak, S. Zhu In a series of heavy-ion inelastic scattering experiments at the ATLAS facility at Argonne and using Gammasphere, the Kπ=2- octupole vibrational rotational bands in 244Pu, 246Cm and 248,250Cf have been populated to high spin, beyond 20 hbar. In all cases, an odd-even staggering pattern was found in the energy of the levels, that increases in amplitude with spin. Both the size of the staggering and its spin dependence appear remarkably consistent with Coriolis-induced two-level mixing with the Kπ=0- band, although the true physics must reflect more indirect interactions involving other orientations of the octupole phonon. |
Tuesday, October 12, 2021 10:30AM - 10:42AM |
DF.00006: Effects of the continuum on the spin-orbit splitting Augusto O Macchiavelli, Christopher M Campbell, Roderick M Clark, Heather L Crawford, Mario Cromaz, Paul Fallon A major step in the development of the shell model was the introduction |
Tuesday, October 12, 2021 10:42AM - 10:54AM |
DF.00007: Enhancing User Experience to Facilitate Nuclear Physics Research through NuDat Donnie Mason The National Nuclear Data Center (NNDC) at Brookhaven National Laboratory (BNL) developed NuDat, a web application where users can explore several databases containing nuclear structure, nuclear decay, and neutron-induced nuclear reaction information. NuDat is the primary web application used to query and visualize nuclear data from the Evaluated Nuclear Structure Data File (ENSDF). ENSDF contains meticulously evaluated recommended values derived from all published experimental nuclear structure and decay data. Over 4 million people use NuDat each year for research, education, and a wide range of applications. The current technology used within NuDat was first developed over 15 years ago and since then significant improvements to web technologies have been made. By modernizing NuDat, the NNDC aims to provide an enhanced user experience that promotes discovery. The modernized NuDat is implemented using HTML Canvas to create a dynamic chart of nuclides. Users can seamlessly interact with over 3,300 nuclides with intuitive pan and zoom gestures. NuDat is accompanied by interactive plots that are similarly controlled. The goal is to create responsive nuclear data visualizations to support future research and uniquely visualize the cornucopia of data that ENSDF has to offer. |
Tuesday, October 12, 2021 10:54AM - 11:06AM |
DF.00008: Symplectic Effective Field Theory David Kekejian, Jerry P Draayer, Kristina D Launey We construct an effective field theory that yields a quantum mechanical Hamiltonian which displays symplectic Sp(3,R) symmetry. We then use this Hamiltonian to study some light nuclei, which demonstrates that it can reproduce B(E2) values without the use of an effective charge, nuclear radii that are in good agreement with experimental data, as well as reasonable excitation spectra. |
Tuesday, October 12, 2021 11:06AM - 11:18AM |
DF.00009: Shapes and Softness in 186W investigated through non-yrast rotational bands P Chowdhury, V.S. Prasher, A.J. Mitchell, M. Albers, C.J. Chiara, M.P. Carpenter, D. Cline, C. Guess, A. Hayes, C.R. Hoffman, R.V.F. Janssnes, B. Kay, T.L. Khoo, A. Korichi, T. Lauritsen, Y. Qiu, D. Seweryniak, S. Tandel, C-Y. Wu, S. Zhu 186W lies in a shape transition region between maximum axial deformation in the rare earth nuclei and spherical 208Pb. The locus of stable nuclei passes through regions of gamma-soft, triaxial and oblate shapes, sometimes coexisting at different spin. This project involved seeking shape changes by exciting stable 186W with 725 and 800MeV 136Xe ions from the ATLAS accelerator at Argonne. Inelastically scattered ions were detected in CHICO2 and de-exciting gamma rays in Gammasphere. Quasi-gamma, quasi-beta and octupole bands were extended considerably. Odd-even staggering in the gamma band suggest the nucleus gets increasingly soft with spin, possibly masking a predicted transition to an oblate shape at high spin. The K=2 octupole band allowed quantification of Coriolis-induced mixing with other bands, especially the Kp=0- band. |
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