29,822 research outputs found
Particles in classically forbidden area, neutron skin and halo, and pure neutron matter in Ca isotopes
The nucleon density distributions and the thickness of pure neutron matter in
Ca isotopes were systematically studied using the Skyrme-Hartree-Fock model
(SHF) from the -stability line to the neutron drip-line. The pure
neutron matter, related with the neutron skin or halo, was shown to depend not
only on the Fermi levels of the neutrons but also on the orbital angular
momentum of the valence neutrons. New definitions for the thickness of pure
neutron matter are proposed.Comment: 6 pages, 5 figure
Green's function method for single-particle resonant states in relativistic mean field theory
Relativistic mean field theory is formulated with the Green's function method
in coordinate space to investigate the single-particle bound states and
resonant states on the same footing. Taking the density of states for free
particle as a reference, the energies and widths of single-particle resonant
states are extracted from the density of states without any ambiguity. As an
example, the energies and widths for single-neutron resonant states in
Sn are compared with those obtained by the scattering phase-shift
method, the analytic continuation in the coupling constant approach, the real
stabilization method and the complex scaling method. Excellent agreements are
found for the energies and widths of single-neutron resonant states.Comment: 20 pages, 7 figure
Microscopic Analysis of Order Parameters in Nuclear Quantum Phase Transitions
Microscopic signatures of nuclear ground-state shape phase transitions in Nd
isotopes are studied using excitation spectra and collective wave functions
obtained by diagonalization of a five-dimensional Hamiltonian for quadrupole
vibrational and rotational degrees of freedom, with parameters determined by
constrained self-consistent relativistic mean-field calculations for triaxial
shapes. As a function of the physical control parameter -- the number of
nucleons, energy gaps between the ground state and the excited vibrational
states with zero angular momentum, isomer shifts, and monopole transition
strengths, exhibit sharp discontinuities at neutron number N=90, characteristic
of a first-order quantum phase transition.Comment: 5 pages, 4 figures, accepted for publication as a Rapid Communication
in Physical Review
Pseudospin symmetry and its approximation in real nuclei
The origin of pseudospin symmetry and its broken in real nuclei are discussed
in the relativistic mean field theory. In the exact pseudospin symmetry, even
the usual intruder orbits have degenerate partners. In real nuclei, pseudospin
symmetry is approximate, and the partners of the usual intruder orbits will
disappear. The difference is mainly due to the pseudo spin-orbit potential and
the transition between them is discussed in details. The contribution of
pseudospin-orbit potential for intruder orbits is quite large, compared with
that for pseudospin doublets. The disappearance of the pseudospin partner for
the intruder orbit can be understood from the properties of its wave function.Comment: 10 pages, 3 figure
The pseudo-spin symmetry in Zr and Sn isotopes from the proton drip line to the neutron drip line
Based on the Relativistic continuum Hartree-Bogoliubov (RCHB) theory, the
pseudo-spin approximation in exotic nuclei is investigated in Zr and Sn
isotopes from the proton drip line to the neutron drip line. The quality of the
pseudo-spin approximation is shown to be connected with the competition between
the centrifugal barrier (CB) and the pseudo-spin orbital potential (PSOP). The
PSOP depends on the derivative of the difference between the scalar and vector
potentials . If , the pseudo-spin symmetry is exact. The
pseudo-spin symmetry is found to be a good approximation for normal nuclei and
to become much better for exotic nuclei with highly diffuse potential, which
have . The energy splitting of the pseudo-spin partners is
smaller for orbitals near the Fermi surface (even in the continuum) than the
deeply bound orbitals. The lower components of the Dirac wave functions for the
pseudo-spin partners are very similar and almost equal in magnitude.Comment: 22 pages, 9figure
Energy Density Functional analysis of shape evolution in N=28 isotones
The structure of low-energy collective states in proton-deficient N=28
isotones is analyzed using structure models based on the relativistic energy
density functional DD-PC1. The relativistic Hartree-Bogoliubov model for
triaxial nuclei is used to calculate binding energy maps in the
- plane. The evolution of neutron and proton single-particle
levels with quadrupole deformation, and the occurrence of gaps around the Fermi
surface, provide a simple microscopic interpretation of the onset of
deformation and shape coexistence. Starting from self-consistent constrained
energy surfaces calculated with the functional DD-PC1, a collective Hamiltonian
for quadrupole vibrations and rotations is employed in the analysis of
excitation spectra and transition rates of Ar, S, and Si.
The results are compared to available data, and previous studies based either
on the mean-field approach or large-scale shell-model calculations. The present
study is particularly focused on S, for which data have recently been
reported that indicate pronounced shape coexistence.Comment: 31 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1102.419
An efficient method for computing the Thouless-Valatin inertia parameters
Starting from the adiabatic time-dependent Hartree-Fock approximation
(ATDHF), we propose an efficient method to calculate the Thouless-Valatin
moments of inertia for the nuclear system. The method is based on the rapid
convergence of the expansion of the inertia matrix. The accuracy of the
proposed method is verified in the rotational case by comparing the results
with the exact Thouless-Valatin moments of inertia calculated using the
self-consistent cranking model. The proposed method is computationally much
more efficient than the full ATDHF calculation, yet it retains a high accuracy
of the order of 1%.Comment: 16 pages, 3 figure
Magnetically Mediated Transparent Conductors: InO doped with Mo
First-principles band structure investigations of the electronic, optical and
magnetic properties of Mo-doped InO reveal the vital role of magnetic
interactions in determining both the electrical conductivity and the
Burstein-Moss shift which governs optical absorption. We demonstrate the
advantages of the transition metal doping which results in smaller effective
mass, larger fundamental band gap and better overall optical transmission in
the visible -- as compared to commercial Sn-doped InO. Similar behavior
is expected upon doping with other transition metals opening up an avenue for
the family of efficient transparent conductors mediated by magnetic
interactions
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Research on VCSEL interference analysis and elimination method
Laser methane gas sensors have been increasingly accepted in coal mine safety monitoring. Most laser spectroscopic methane gas sensors are based in BFB lasers at around 1650nm. However, they suffer from high power consumption and high cost due to temperature control is required for laser diode operation at constant temperature. VCSEL lasers have offered low operation current and low power consumption when operating at non-TEC mode. However, it is found that the interference noise is critical for laser methane detection. This paper report typical results of the laser diode ripple characterization method and methods of noise reduction methods are discussed
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