2,289,771 research outputs found
Narrowing of spectral lines beyond the natural or dephasing line width
Transient excitation and gated or delayed observation provides a narrowing of the inherent line width of the transition. Possible experimental one- and two-photon systems are discussed and the loss of signal with line narrowing is calculated. The general case of lines broadened by dephasing processes is treated. Contact is made with the line narrowing in recent Raman type experiments
Structure of Critical Lines in Quenched Lattice QCD with the Wilson Quark Action
The structure of critical lines of vanishing pion mass for the Wilson quark
action is examined in quenched lattice QCD. The numerical evidence is presented
that critical lines spread into five branches beyond beta=5.6-5.7 at zero
temperature. It is also shown that critical lines disappear in the deconfined
phase for the case of finite temperatures.Comment: 11 pages, Latex, 7 Postscript figures, uses epsf.st
Systematic study of deformed nuclei at the drip lines and beyond
An improved prescription for choosing a transformed harmonic oscillator (THO)
basis for use in configuration-space Hartree-Fock-Bogoliubov (HFB) calculations
is presented. The new HFB+THO framework that follows accurately reproduces the
results of coordinate-space HFB calculations for spherical nuclei, including
those that are weakly bound. Furthermore, it is fully automated, facilitating
its use in systematic investigations of large sets of nuclei throughout the
periodic table. As a first application, we have carried out calculations using
the Skyrme Force SLy4 and volume pairing, with exact particle number projection
following application of the Lipkin-Nogami prescription. Calculations were
performed for all even-even nuclei from the proton drip line to the neutron
drip line having proton numbers Z=2,4,...,108 and neutron numbers
N=2,4,...,188. We focus on nuclei near the neutron drip line and find that
there exist numerous particle-bound even-even nuclei (i.e., nuclei with
negative Fermi energies) that have at the same time negative two-neutron
separation energies. This phenomenon, which was earlier noted for light nuclei,
is attributed to bound shape isomers beyond the drip line.Comment: 12 ReVTeX4 pages, 6 EPS figures. See also
http://www.fuw.edu.pl/~dobaczew/thodri/thodri.htm
Dislocation lines as the precursor of the melting of crystalline solids observed in Monte Carlo simulations
The microscopic mechanism of the melting of a crystal is analyzed by the
constant pressure Monte Carlo simulation of a Lennard-Jones fcc system. Beyond
a temperature of the order of 0.8 of the melting temperature, we found that the
relevant excitations are lines of defects. Each of these lines has the
structure of a random walk of various lengths on an fcc defect lattice. We
identify these lines with the dislocation ones proposed in recent
phenomenological theories of melting. Near melting we find the appearance of
long lines that cross the whole system. We suggest that these long lines are
the precursor of the melting process.Comment: 5 pages, 5 figures, accepted in Physical Review Letter
Abundances of s-process elements in planetary nebulae: Br, Kr & Xe
We identify emission lines of post-iron peak elements in very high
signal-to-noise spectra of a sample of planetary nebulae. Analysis of lines
from ions of Kr and Xe reveals enhancements in most of the PNe, in agreement
with the theories of s-process in AGB star. Surprisingly, we did not detect
lines from Br even though s-process calculations indicate that it should be
produced with Kr at detectable levels.Comment: 2 pages, 1 figure, to be published in the Proceedings of the IAU
Symposium 234: Planetary Nebulae in Our Galaxy and Beyond, eds. M.J. Barlow,
R.H. Mende
Fe/Ni ratio in the Ant Nebula Mz 3
We have analyzed the [Fe II] and [Ni II] emission lines in the bipolar
planetary nebula Mz~3. We find that the [Fe II] and [Ni II] lines arise
exclusively from the central regions. Fluorescence excitation in the formation
process of these lines is negligible for this low-excitation nebula. From the
[Fe II]/[Ni II] ratio, we obtain a higher Fe/Ni abundance ratio with respect to
the solar value. The current result provides further supporting evidence for Mz
3 as a symbiotic Mira.Comment: 2 pages, 1 figure, to be published in the Proceedings of the IAU
Symposium 234: Planetary Nebulae in Our Galaxy and Beyond, eds. M.J. Barlow,
R.H. Mende
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