197 research outputs found
Spin-dependent observables in surrogate reactions
Observables emitted from various spin states in compound U nuclei are
investigated to validate usefulness of the surrogate reaction method. It was
found that energy spectrum of cascading -rays and their multiplicities,
spectrum of evaporated neutrons, and mass-distribution of fission fragments
show clear dependence on the spin of decaying nuclei. The present results
indicate that they can be used to infer populated spin distributions which
significantly affect the decay branching ratio of the compound system produced
by the surrogate reactions
On the 3n+l Quantum Number in the Cluster Problem
It has recently been suggested that an exactly solvable problem characterized
by a new quantum number may underlie the electronic shell structure observed in
the mass spectra of medium-sized sodium clusters. We investigate whether the
conjectured quantum number 3n+l bears a similarity to the quantum numbers n+l
and 2n+l, which characterize the hydrogen problem and the isotropic harmonic
oscillator in three dimensions.Comment: 8 pages, revtex, 4 eps figures included, to be published in
Phys.Rev.A, additional material available at
http://radix2.mpi-stuttgart.mpg.de/koch/Diss
Formation of two-dimensional weak localization in conducting Langmuir-Blodgett films
We report the magnetotransport properties up to 7 T in the organic highly
conducting Langmuir-Blodgett(LB) films formed by a molecular association of the
electroactive donor molecule bis(ethylendioxy)tetrathiafulvalene (BEDO-TTF) and
stearic acid CH(CH)COOH. We show the logarithmic decrease of dc
conductivity and the negative transverse magnetoresistance at low temperature.
They are interpreted in the weak localization of two-dimensional (2D)
electronic system based on the homogeneous conducting layer with the molecular
size thickness of BEDO-TTF. The electronic length with phase memory is given at
the mesoscopic scale, which provides for the first time evidence of the 2D
coherent charge transport in the conducting LB films.Comment: 5 pages, 1 Table and 5 figure
Unified description of magic numbers of metal clusters in terms of the 3-dimensional q-deformed harmonic oscillator
Magic numbers predicted by a 3-dimensional q-deformed harmonic oscillator
with Uq(3)>SOq(3) symmetry are compared to experimental data for atomic
clusters of alkali metals (Li, Na, K, Rb, Cs), noble metals (Cu, Ag, Au),
divalent metals (Zn, Cd), and trivalent metals (Al, In), as well as to
theoretical predictions of jellium models, Woods-Saxon and wine bottle
potentials, and to the classification scheme using the 3n+l pseudo quantum
number. In alkali metal clusters and noble metal clusters the 3-dimensional
q-deformed harmonic oscillator correctly predicts all experimentally observed
magic numbers up to 1500 (which is the expected limit of validity for theories
based on the filling of electronic shells), while in addition it gives
satisfactory results for the magic numbers of clusters of divalent metals and
trivalent metals, thus indicating that Uq(3), which is a nonlinear extension of
the U(3) symmetry of the spherical (3-dimensional isotropic) harmonic
oscillator, is a good candidate for being the symmetry of systems of several
metal clusters. The Taylor expansions of angular momentum dependent potentials
approximately producing the same spectrum as the 3-dimensional q-deformed
harmonic oscillator are found to be similar to the Taylor expansions of the
symmetrized Woods-Saxon and wine-bottle symmetrized Woods-Saxon potentials,
which are known to provide successful fits of the Ekardt potentials.Comment: 23 pages including 7 table
Nuclear Ground State Observables and QCD Scaling in a Refined Relativistic Point Coupling Model
We present results obtained in the calculation of nuclear ground state
properties in relativistic Hartree approximation using a Lagrangian whose
QCD-scaled coupling constants are all natural (dimensionless and of order 1).
Our model consists of four-, six-, and eight-fermion point couplings (contact
interactions) together with derivative terms representing, respectively, two-,
three-, and four-body forces and the finite ranges of the corresponding mesonic
interactions. The coupling constants have been determined in a self-consistent
procedure that solves the model equations for representative nuclei
simultaneously in a generalized nonlinear least-squares adjustment algorithm.
The extracted coupling constants allow us to predict ground state properties of
a much larger set of even-even nuclei to good accuracy. The fact that the
extracted coupling constants are all natural leads to the conclusion that QCD
scaling and chiral symmetry apply to finite nuclei.Comment: 44 pages, 13 figures, 9 tables, REVTEX, accepted for publication in
Phys. Rev.
Relativistic Nuclear Energy Density Functionals: Mean-Field and Beyond
Relativistic energy density functionals (EDF) have become a standard tool for
nuclear structure calculations, providing a complete and accurate, global
description of nuclear ground states and collective excitations. Guided by the
medium dependence of the microscopic nucleon self-energies in nuclear matter,
semi-empirical functionals have been adjusted to the nuclear matter equation of
state and to bulk properties of finite nuclei, and applied to studies of
arbitrarily heavy nuclei, exotic nuclei far from stability, and even systems at
the nucleon drip-lines. REDF-based structure models have also been developed
that go beyond the static mean-field approximation, and include collective
correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. These models are employed in analyses of
structure phenomena related to shell evolution, including detailed predictions
of excitation spectra and electromagnetic transition rates.Comment: To be published in Progress in Particle and Nuclear Physic
Level and Eigenfunction Statistics in Billiards with Surface Scattering
Statistical properties of billiards with diffusive boundary scattering are
investigated by means of the supersymmetric sigma-model in a formulation
appropriate for chaotic ballistic systems. We study level statistics,
parametric level statistics, and properties of electron wavefunctions. In the
universal regime, our results reproduce conclusions of the random matrix
theory, while beyond this regime we obtain a variety of system-specific results
determined by the classical dynamics in the billiard. Most notably, we find
that level correlations do not vanish at arbitrary separation between energy
levels, or if measured at arbitrarily large difference of magnetic fields.
Saturation of the level number variance indicates strong rigidity of the
spectrum. To study spatial correlations of wavefunction amplitudes, we
reanalyze and refine derivation of the ballistic version of the sigma-model.
This allows us to obtain a proper matching of universal short-scale
correlations with system-specific ones.Comment: 19 pages, 5 figures included. Minor corrections, references adde
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