240 research outputs found
Garvey-Kelson Relations for Nuclear Charge Radii
The Garvey-Kelson relations (GKRs) are algebraic expressions originally
developed to predict nuclear masses. In this letter we show that the GKRs
provide a fruitful framework for the prediction of other physical observables
that also display a slowly-varying dynamics. Based on this concept, we extend
the GKRs to the study of nuclear charge radii. The GKRs are tested on 455 out
of the approximately 800 nuclei whose charge radius is experimentally known. We
find a rms deviation between the GK predictions and the experimental values of
only 0.01 fm. This should be contrasted against some of the most successful
microscopic models that yield rms deviations almost three times as large.
Predictions - with reliable uncertainties - are provided for 116 nuclei whose
charge radius is presently unknown.Comment: 4 pages and 3 figure
Saturation properties and incompressibility of nuclear matter: A consistent determination from nuclear masses
Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant =1.138 fm and binding energy per nucleon = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility to be 288 28 MeV using
the same source of nuclear masses as input.Comment: 14 latex pages, five figures available on request ( to appear in Phy.
Rev. C
Charge radii and structural evolution in Sr, Zr, and Mo isotopes
The evolution of the ground-state nuclear shapes in neutron-rich Sr, Zr, and
Mo isotopes, including both even-even and odd-A nuclei, is studied within a
self-consistent mean-field approximation based on the D1S Gogny interaction.
Neutron separation energies and charge radii are calculated and compared with
available data. A correlation between a shape transition and a discontinuity in
those observables is found microscopically. While in Sr and Zr isotopes the
steep behavior observed in the isotopic dependence of the charge radii is a
consequence of a sharp prolate-oblate transition, the smooth behavior found in
Mo isotopes has its origin in an emergent region of triaxiality.Comment: 6 pages, 7 figures, to be published in Phys. Lett.
Evidence of sound production by spawning lake trout (Salvelinus namaycush) in lakes Huron and Champlain
Two sounds associated with spawning lake trout (Salvelinus namaycush) in lakes Huron and Champlain were characterized by comparing sound recordings with behavioral data collected using acoustic telemetry and video. These sounds were named “growls” and “snaps” and were heard on lake trout spawning reefs, but not on a nonspawning reef, and were more common at night than during the day. Growls also occurred more often during the spawning period than the prespawning period, while the trend for snaps was reversed. In a laboratory flume, sounds occurred when male lake trout were displaying spawning behaviors: growls when males were quivering and parallel swimming and snaps when males moved their jaw. Combining our results with the observation of possible sound production by spawning splake (Salvelinus fontinalis × Salvelinus namaycush hybrid) provides rare evidence for spawning-related sound production by a salmonid or any other fish in the superorder Protacanthopterygii. Further characterization of these sounds could be useful for lake trout assessment, restoration, and control
Studies of neutron-rich nuclei using the CPT mass spectrometer at CARIBU
The nucleosynthetic path of the astrophysical r-process and the resulting elemental abundances depend on neutron-separation energies which can be determined from the masses of the nuclei along the r-process reaction path. Due to the current lack of experimental data, mass models are often used. The mass values provided by the mass models are often too imprecise or disagree with each other. Therefore, direct high-precision mass measurements of neutron-rich nuclei are necessary to provide input parameters to the calculations and help refine the mass models. The Californium Rare Isotope Breeder Upgrade (CARIBU) facility of Argonne National Laboratory will provide experiments with beams of short-lived neutron-rich nuclei. The Canadian Penning Trap (CPT) mass spectrometer has been relocated to the CARIBU low-energy beam line to extend measurements of the neutron-rich nuclei into the mostly unexplored region along the r-process path. This will allow precise mass measurements (∼ 10 keV/c2) of more than a hundred very neutron-rich isotopes that have not previously been measured
The use of cosmic-ray muons in the energy calibration of the Beta-decay Paul Trap silicon-detector array
This article presents an approach to calibrate the energy response of double-sided silicon strip detectors (DSSDs) for low-energy nuclear-science experiments by utilizing cosmic-ray muons. For the 1-mm-thick detectors used with the Beta-decay Paul Trap, the minimum-ionizing peak from these muons provides a stable and time-independent in situ calibration point at around 300 keV, which supplements the calibration data obtained above 3 MeV from α sources. The muon-data calibration is achieved by comparing experimental spectra with detailed Monte Carlo simulations performed using GEANT4 and CRY codes. This additional information constrains the calibration at lower energies, resulting in improvements in quality and accuracy
β-delayed neutron spectroscopy using trapped radioactive ions
A novel technique for β-delayed neutron spectroscopy has been demonstrated using trapped ions. The neutron-energy spectrum is reconstructed by measuring the time of flight of the nuclear recoil following neutron emission, thereby avoiding all the challenges associated with neutron detection, such as backgrounds from scattered neutrons and γ rays and complicated detector-response functions. I+137 ions delivered from a Cf252 source were confined in a linear Paul trap surrounded by radiation detectors, and the β-delayed neutron-energy spectrum and branching ratio were determined by detecting the β- and recoil ions in coincidence. Systematic effects were explored by determining the branching ratio three ways. Improvements to achieve higher detection efficiency, better energy resolution, and a lower neutron-energy threshold are proposed. © 2013 American Physical Society
Tensor interaction limit derived from the α-β-ν̄ correlation in trapped Li8 ions
A measurement of the α-β-ν̄ angular correlation in the Gamow-Teller decay Li8→Be*8+ν̄+β, Be*8→ α+α has been performed using ions confined in a linear Paul trap surrounded by silicon detectors. The energy difference spectrum of the α particles emitted along and opposite the direction of the β particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component CT relative to that of the dominant axial-vector component CA of the electroweak interaction is limited to |CT/CA|\u3c0.18 (95.5% confidence level). This experimental approach is facilitated by several favorable features of the Li8 β decay and has different systematic effects than the previous β-ν̄ correlation results for a pure Gamow-Teller transition obtained from studying He6 β decay. © 2013 American Physical Society
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