3,896 research outputs found
Dynamic elastic properties and magnetic susceptibility across the austenite-martensite transformation in site-disordered ferromagnetic Ni-Fe-Al alloy
Besides permitting an accurate determination of the
ferromagnetic-to-paramagnetic phase transition temperature and the
characteristic temperatures for the beginning and end of the growth of
martensite (austenite) phase at the expense of austenite (martensite) phase
while cooling (heating), the results of an extensive ac susceptibility, sound
velocity and internal friction investigation of the thermoelastic martensitic
transformation in melt-quenched (site-disordered) Ni55Fe20Al25 alloy provide a
clear experimental evidence for the following. Irreversible thermoelastic
changes (thermal hysteresis) occur in the austenite phase in the premartensitic
regime. In the heating cycle, the system retains the "memory" of the initiation
and subsequent growth of the martensitic phase (at the expense of the parent
austenite phase) that had taken place during the cooling cycle in the
austenite-martensite phase coexistence region. We report and discuss these
novel findings in this communication.Comment: 5 figure
Quadrupole Collective Dynamics from Energy Density Functionals: Collective Hamiltonian and the Interacting Boson Model
Microscopic energy density functionals (EDF) have become a standard tool for
nuclear structure calculations, providing an accurate global description of
nuclear ground states and collective excitations. For spectroscopic
applications this framework has to be extended to account for collective
correlations related to restoration of symmetries broken by the static mean
field, and for fluctuations of collective variables. In this work we compare
two approaches to five-dimensional quadrupole dynamics: the collective
Hamiltonian for quadrupole vibrations and rotations, and the Interacting Boson
Model. The two models are compared in a study of the evolution of non-axial
shapes in Pt isotopes. Starting from the binding energy surfaces of
Pt, calculated with a microscopic energy density functional, we
analyze the resulting low-energy collective spectra obtained from the
collective Hamiltonian, and the corresponding IBM-2 Hamiltonian. The calculated
excitation spectra and transition probabilities for the ground-state bands and
the -vibration bands are compared to the corresponding sequences of
experimental states.Comment: 10 pages, 4 figures; to be published in Phys. Rev.
Ingredients of nuclear matrix element for two-neutrino double-beta decay of 48Ca
Large-scale shell model calculations including two major shells are carried
out, and the ingredients of nuclear matrix element for two-neutrino double beta
decay are investigated. Based on the comparison between the shell model
calculations accounting only for one major shell (-shell) and those for two
major shells (-shell), the effect due to the excitation across the two
major shells is quantitatively evaluated.Comment: To appear in J. Phys. Soc. Conf. Proc. (ARIS2014); for ver.2, Fig.1
is revise
Benchmark calculation of no-core Monte Carlo shell model in light nuclei
The Monte Carlo shell model is firstly applied to the calculation of the
no-core shell model in light nuclei. The results are compared with those of the
full configuration interaction. The agreements between them are within a few %
at most.Comment: 4 pages, 1 figure, 1 table, Proceedings of the International
Symposium on New Faces of Atomic Nuclei, Okinawa, Japan, Nov. 15-17, 201
CO J = 2 - 1 Emission from Evolved Stars in the Galactic Bulge
We observe a sample of 8 evolved stars in the Galactic Bulge in the CO J = 2
- 1 line using the Submillimeter Array (SMA) with angular resolution of 1 - 4
arcseconds. These stars have been detected previously at infrared wavelengths,
and several of them have OH maser emission. We detect CO J = 2 - 1 emission
from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and
[SLO2003] A51. We do not detect the remaining 5 stars in the sample because of
heavy contamination from the galactic foreground CO emission. Combining CO data
with observations at infrared wavelengths constraining dust mass loss from
these stars, we determine the gas-to-dust ratios of the Galactic Bulge stars
for which CO emission is detected. For OH 359.943 +0.260, we determine a gas
mass-loss rate of 7.9 (+/- 2.2) x 10^-5 M_Sun/year and a gas-to-dust ratio of
310 (+/- 89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 (+/- 2.8)
x 10^-5 M_Sun/year and a gas-to-dust ratio of 220 (+/- 110). For [SLO2003] A51,
we find a gas mass-loss rate of 3.4 (+/- 3.0) x 10^-5 M_Sun/year and a
gas-to-dust ratio of 160 (+/- 140), reflecting the low quality of our tentative
detection of the CO J = 2 - 1 emission from A51. We find the CO J = 2 - 1
detections of OH/IR stars in the Galactic Bulge require lower average CO J = 2
- 1 backgrounds.Comment: 40 pages, 16 figures, appeared in the 1 March 2013 issue of the
Astrophysical Journa
Structural evolution in Pt isotopes with the Interacting Boson Model Hamiltonian derived from the Gogny Energy Density Functional
Spectroscopic calculations are carried out, for the description of the
shape/phase transition in Pt nuclei in terms of the Interacting Boson Model
(IBM) Hamiltonian derived from (constrained) Hartree-Fock-Bogoliubov (HFB)
calculations with the finite range and density dependent Gogny-D1S Energy
Density Functional. Assuming that the many-nucleon driven dynamics of nuclear
surface deformation can be simulated by effective bosonic degrees of freedom,
the Gogny-D1S potential energy surface (PES) with quadrupole degrees of freedom
is mapped onto the corresponding PES of the IBM. Using this mapping procedure,
the parameters of the IBM Hamiltonian, relevant to the low-lying quadrupole
collective states, are derived as functions of the number of valence nucleons.
Merits of both Gogny-HFB and IBM approaches are utilized so that the spectra
and the wave functions in the laboratory system are calculated precisely. The
experimental low-lying spectra of both ground-state and side-band levels are
well reproduced. From the systematics of the calculated spectra and the reduced
E2 transition probabilities (E2), the prolate-to-oblate shape/phase
transition is shown to take place quite smoothly as a function of neutron
number in the considered Pt isotopic chain, for which the -softness
plays an essential role. All these spectroscopic observables behave
consistently with the relevant PESs and the derived parameters of the IBM
Hamiltonian as functions of . Spectroscopic predictions are also made for
those nuclei which do not have enough experimental E2 data.Comment: 11 pages, 5 figure
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