161 research outputs found
Structure properties of Th and Fm fission fragments: mean field analysis with the Gogny force
The constrained Hartree-Fock-Bogoliubov method is used with the Gogny
interaction D1S to calculate potential energy surfaces of fissioning nuclei
Th and Fm up to very large deformations. The
constraints employed are the mass quadrupole and octupole moments. In this
subspace of collective coordinates, many scission configurations are identified
ranging from symmetric to highly asymmetric fragmentations. Corresponding
fragment properties at scission are derived yielding fragment deformations,
deformation energies, energy partitioning, neutron binding energies at
scission, neutron multiplicities, charge polarization and total fragment
kinetic energies.Comment: 15 pages, 23 figures, accepted for publication in Phys. Rev. C (2007
The low-lying quadrupole collective excitations of Ru and Pd isotopes
Quadrupole excitations of even-even Ru and Pd isotopes are described within
microscopic approach based on the general collective Bohr model which includes
the effect of coupling with the pairing vibrations. The excitation energies and
E2 transition probabilities observed in 104-114Ru and 106-110Pd are reproduced
in the frame of the calculation containing no free parameters.Comment: 11 pages, 18 figures in EPS forma
Collective quadrupole excitations in the 50<Z,N<82 nuclei with the generalized Bohr Hamiltonian
The generalized Bohr Hamiltonian is applied to a description of low-lying
collective excitations in even-even isotopes of Te, Xe, Ba, Ce, Nd and Sm. The
collective potential and inertial functions are determined by means of the
Strutinsky method and the cranking model, respectively. A shell-dependent
parametrization of the Nilsson potential is used. An approximate
particle-number projection is performed in treatment of pairing correlations.
The effect of coupling with the pairing vibrations is taken into account
approximately when determining the inertial functions. The calculation does not
contain any free parameter.Comment: Latex2e source, 20 pages, 14 figures in EPS format, tar gzipped fil
Measuring processes and the Heisenberg picture
In this paper, we attempt to establish quantum measurement theory in the
Heisenberg picture. First, we review foundations of quantum measurement theory,
that is usually based on the Schr\"{o}dinger picture. The concept of instrument
is introduced there. Next, we define the concept of system of measurement
correlations and that of measuring process. The former is the exact counterpart
of instrument in the (generalized) Heisenberg picture. In quantum mechanical
systems, we then show a one-to-one correspondence between systems of
measurement correlations and measuring processes up to complete equivalence.
This is nothing but a unitary dilation theorem of systems of measurement
correlations. Furthermore, from the viewpoint of the statistical approach to
quantum measurement theory, we focus on the extendability of instruments to
systems of measurement correlations. It is shown that all completely positive
(CP) instruments are extended into systems of measurement correlations. Lastly,
we study the approximate realizability of CP instruments by measuring processes
within arbitrarily given error limits.Comment: v
Egorov's theorem for transversally elliptic operators on foliated manifolds and noncommutative geodesic flow
The main result of the paper is Egorov's theorem for transversally elliptic
operators on compact foliated manifolds. This theorem is applied to describe
the noncommutative geodesic flow in noncommutative geometry of Riemannian
foliations.Comment: 23 pages, no figures. Completely revised and improved version of
dg-ga/970301
A Photonic Atom Probe coupling 3D Atomic Scale Analysis with in situ Photoluminescence Spectroscopy
Laser enhanced field evaporation of surface atoms in Laser-assisted Atom
Probe Tomography (La-APT) can simultaneously excite phtotoluminescence in
semiconductor or insulating specimens. An atom probe equipped with appropriate
focalization and collection optics has been coupled with an in-situ
micro-Photoluminescence ({\mu}PL) bench that can be operated during APT
analysis. The Photonic Atom Probe instrument we have developped operates at
frequencies up to 500 kHz and is controlled by 150 fs laser pulses tunable in
energy in a large spectral range (spanning from deep UV to near IR). Micro-PL
spectroscopy is performed using a 320 mm focal length spectrometer equipped
with a CCD camera for time-integrated and with a streak camera for
time-resolved acquisitions. An exemple of application of this instrument on a
multi-quantum well oxide heterostructure sample illustrates the potential of
this new generation of tomographic atom probe.Comment: 22 pages, 4 figures. The following article has been accepted by the
Review of Scientific Instruments. After it is published, it will be found at
https://publishing.aip.org/resources/librarians/products/journals
The nuclear energy density functional formalism
The present document focuses on the theoretical foundations of the nuclear
energy density functional (EDF) method. As such, it does not aim at reviewing
the status of the field, at covering all possible ramifications of the approach
or at presenting recent achievements and applications. The objective is to
provide a modern account of the nuclear EDF formalism that is at variance with
traditional presentations that rely, at one point or another, on a {\it
Hamiltonian-based} picture. The latter is not general enough to encompass what
the nuclear EDF method represents as of today. Specifically, the traditional
Hamiltonian-based picture does not allow one to grasp the difficulties
associated with the fact that currently available parametrizations of the
energy kernel at play in the method do not derive from a genuine
Hamilton operator, would the latter be effective. The method is formulated from
the outset through the most general multi-reference, i.e. beyond mean-field,
implementation such that the single-reference, i.e. "mean-field", derives as a
particular case. As such, a key point of the presentation provided here is to
demonstrate that the multi-reference EDF method can indeed be formulated in a
{\it mathematically} meaningful fashion even if does {\it not} derive
from a genuine Hamilton operator. In particular, the restoration of symmetries
can be entirely formulated without making {\it any} reference to a projected
state, i.e. within a genuine EDF framework. However, and as is illustrated in
the present document, a mathematically meaningful formulation does not
guarantee that the formalism is sound from a {\it physical} standpoint. The
price at which the latter can be enforced as well in the future is eventually
alluded to.Comment: 64 pages, 8 figures, submitted to Euroschool Lecture Notes in Physics
Vol.IV, Christoph Scheidenberger and Marek Pfutzner editor
Application of Multiple Scattering Theory to Lower Energy Elastic Nucleon-Nucleus Reactions
The optical model potentials for nucleon-nucleus elastic scattering at
~MeV are calculated for C, O, Si, Ca,
Fe, Zr and Pb in first order multiple scattering theory,
following the prescription of the spectator expansion, where the only inputs
are the free NN potentials, the nuclear densities and the nuclear mean field as
derived from microscopic nuclear structure calculations. These potentials are
used to predict differential cross sections, analyzing powers and spin rotation
functions for neutron and proton scattering at 65 MeV projectile energy and
compared with available experimental data.Comment: 12 pages (Revtex 3.0), 7 fig
- …