443 research outputs found
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Nuclear structure studies of medium-mass nuclei using large Ge arrays
The advent of large Ge arrays and their ancillary detectors has greatly advanced spectroscopic studies of the medium-mass nuclei. These nuclei undergo rapid shape changes as a function of spin, excitation energy and particle number and, thus, provide a unique laboratory to test and refine a variety of theoretical models. Following a brief review of the physics motivation, some of the highlights of the experimental results obtained with the help of these powerful detector systems will be discussed. Among results presented here are the newly-discovered island of superdeformation in the A{approximately}80 mass region, and the high-spin band structures in the N{approximately}Z nuclei. These band structures may be understood in the framework of the conventional cranking models, without the introduction of additional T=0 neutron-proton pairing correlations
Diffusion of Lithium Ions in Lithium-Argyrodite Solid-State Electrolytes from Equilibrium and Nonequilibrium Molecular Dynamics Simulations
The use of solid-state electrolytes to provide safer, next-generation
rechargeable batteries is becoming more feasible as new materials with greater
stability and higher ionic diffusion coefficients are designed. However,
accurate determination of diffusion coefficients in solids is problematic and
reliable calculations are highly sought-after. In this paper we compare
diffusion coefficients calculated using nonequilibrium and equilibrium ab
initio molecular dynamics simulations for highly diffusive solid-state
electrolytes for the first time, to demonstrate the accuracy that can be
obtained. Moreover, we show that ab initio nonequilibrium molecular dynamics
can be used to determine diffusion coefficients when the diffusion is too slow
for it to be feasible to obtain them using ab initio equilibrium simulations.
Thereby, using ab initio nonequilibrium molecular dynamics simulations we are
able to obtain accurate estimates of the diffusion coefficients of Li ions in
LiPSCl and LiPSCl, two promising electrolytes for
all-solid-state batteries. Furthermore, these calculations show that the
diffusion coefficient of lithium ions in LiPSCl is higher than many
other potential all-solid-state electrolytes, making it promising for future
technologies. The reasons for variation in conductivities determined using
computational and experimental methods are also discussed. It is demonstrated
that small degrees of disorder and vacancies can result in orders of magnitude
differences in diffusivities of Li ions in LiPSCl, and these factors
are likely to contribute to inconsistencies observed in experimentally reported
values. Notably, the introduction of Li-vacancies and disorder can enhance the
ionic conductivity of LiPSCl.Comment: 32 pages, 8 figures, 2 table
Prompt Alpha Decay of a Well-deformed Band in 58Ni
Two excited well-deformed bands have been observed in the semi-magic nucleus Ni-58. One of the bands was observed to partially decay by emission of a prompt discrete alpha particle that feeds the 2949 keV 6(+) spherical yrast state in the daughter nucleus Fe-54. This constitutes the first observation of prompt alpha emission from states lying in the deformed secondary minimum of the nuclear potential. gamma -ray linking transitions via several parallel paths establish the spin. parity, and excitation energy of this deformed band in Ni-58
Prompt Alpha Decay of a Well-deformed Band in 58Ni
Two excited well-deformed bands have been observed in the semi-magic nucleus Ni-58. One of the bands was observed to partially decay by emission of a prompt discrete alpha particle that feeds the 2949 keV 6(+) spherical yrast state in the daughter nucleus Fe-54. This constitutes the first observation of prompt alpha emission from states lying in the deformed secondary minimum of the nuclear potential. gamma -ray linking transitions via several parallel paths establish the spin. parity, and excitation energy of this deformed band in Ni-58
Tests and applications of self-consistent cranking in the interacting boson model
The self-consistent cranking method is tested by comparing the cranking
calculations in the interacting boson model with the exact results obtained
from the SU(3) and O(6) dynamical symmetries and from numerical
diagonalization. The method is used to study the spin dependence of shape
variables in the and boson models. When realistic sets of parameters
are used, both models lead to similar results: axial shape is retained with
increasing cranking frequency while fluctuations in the shape variable
are slightly reduced.Comment: 9 pages, 3 ps figures, Revte
Magnetic moments of 2 1 + states in 124,126,128 Sn
The g factors of the first-excited states of stable 124Sn and radioactive 126,128Sn were measured by the recoil-in-vacuum method with comparatively high precision. The experiments were performed at the Holifield Radioactive Ion Beam Facility by Coulomb e
Time-odd components in the mean field of rotating superdeformed nuclei
Rotation-induced time-odd components in the nuclear mean field are analyzed
using the Hartree-Fock cranking approach with effective interactions SIII,
SkM*, and SkP. Identical dynamical moments are obtained for
pairs of superdeformed bands Tb(2)--Dy(1) and
Gd(2)--Tb(1). The corresponding relative alignments strongly
depend on which time-odd mean-field terms are taken into account in the
Hartree-Fock equations.Comment: 23 pages, ReVTeX, 6 uuencoded postscript figures include
First-excited state g factor of Te 136 by the recoil in vacuum method
The g factor of the first 2+ state of radioactive 136Te with two valence protons and two valence neutrons beyond double-magic 132Sn has been measured by the recoil in vacuum (RIV) method. The lifetime of this state is an order of magnitude longer than the lifetimes of excited states recently measured by the RIV method in Sn and Te isotopes, requiring a new evaluation of the free-ion hyperfine interactions and methodology used to determine the g factor. The calibration data are reported and the analysis procedures are described in detail. The resultant g factor has a similar magnitude to the g factors of other nuclei with an equal number of valence protons and neutrons in the major shell. However, an unexpected trend is found in the g factors of the N=84 isotones, which decrease from 136Te to 144Nd. Shell model calculations with interactions derived from the CD Bonn potential show good agreement with the g factors and E2 transition rates of 2+ states around 132Sn, confirming earlier indications that 132Sn is a good doubly magic core
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Study of spin-temperature effects using energy-ordered continuum gamma-ray spectroscopy technique
We have investigated a new continuum {gamma}-ray spectroscopy technique which is based on the detection of all emitted {gamma} rays in a 4{pi} detector system, and ordering them according to their energies on an event-by-event basis. The technique allows determination of gamma strength functions, and rotational damping width as a function of spin and temperature. Thus, it opens up the possibility of studying the onset of motional narrowing, order-to-chaos transition, and the mapping of the evolution of nuclear collectivity with a spin and temperature. Application of the technique for preferential entry-state population, exit-channel selection, and feeding of the discrete states via selective pathways will be discussed. 20 refs., 4 figs
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