229,658 research outputs found
Classical Trajectory Perspective on Double Ionization Dynamics of Diatomic Molecules Irradiated by Ultrashort Intense Laser Pulses
In the present paper, we develop a semiclassical quasi-static model
accounting for molecular double ionization in an intense laser pulse. With this
model, we achieve insight into the dynamics of two highly-correlated valence
electrons under the combined influence of a two-center Coulomb potential and an
intense laser field, and reveal the significant influence of molecular
alignment on the ratio of double over single ion yield. Analysis on the
classical trajectories unveils sub-cycle dynamics of the molecular double
ionization. Many interesting features, such as the accumulation of emitted
electrons in the first and third quadrants of parallel momentum plane, the
regular pattern of correlated momentum with respect to the time delay between
closest collision and ionization moment, are revealed and successfully
explained by back analyzing the classical trajectories. Quantitative agreement
with experimental data over a wide range of laser intensities from tunneling to
over-the-barrier regime is presented.Comment: 8 pages, 9 figure
Exploring Quantum Phase Transitions with a Novel Sublattice Entanglement Scenario
We introduce a new measure called reduced entropy of sublattice to quantify
entanglement in spin, electron and boson systems. By analyzing this quantity,
we reveal an intriguing connection between quantum entanglement and quantum
phase transitions in various strongly correlated systems: the local extremes of
reduced entropy and its first derivative as functions of the coupling constant
coincide respectively with the first and second order transition points. Exact
numerical studies merely for small lattices reproduce several well-known
results, demonstrating that our scenario is quite promising for exploring
quantum phase transitions.Comment: 4 pages, 4 figure
Symmetries and Lie algebra of the differential-difference Kadomstev-Petviashvili hierarchy
By introducing suitable non-isospectral flows we construct two sets of
symmetries for the isospectral differential-difference Kadomstev-Petviashvili
hierarchy. The symmetries form an infinite dimensional Lie algebra.Comment: 9 page
Ab Initio Simulation of the Nodal Surfaces of Heisenberg Antiferromagnets
The spin-half Heisenberg antiferromagnet (HAF) on the square and triangular
lattices is studied using the coupled cluster method (CCM) technique of quantum
many-body theory. The phase relations between different expansion coefficients
of the ground-state wave function in an Ising basis for the square lattice HAF
is exactly known via the Marshall-Peierls sign rule, although no equivalent
sign rule has yet been obtained for the triangular lattice HAF. Here the CCM is
used to give accurate estimates for the Ising-expansion coefficients for these
systems, and CCM results are noted to be fully consistent with the
Marshall-Peierls sign rule for the square lattice case. For the triangular
lattice HAF, a heuristic rule is presented which fits our CCM results for the
Ising-expansion coefficients of states which correspond to two-body excitations
with respect to the reference state. It is also seen that Ising-expansion
coefficients which describe localised, -body excitations with respect to the
reference state are found to be highly converged, and from this result we infer
that the nodal surface of the triangular lattice HAF is being accurately
modeled. Using these results, we are able to make suggestions regarding
possible extensions of existing quantum Monte Carlo simulations for the
triangular lattice HAF.Comment: 24 pages, Latex, 3 postscript figure
On linear coupling of acoustic and cyclotron waves in plasma flows
It is found that in magnetized electrostatic plasma flows the velocity shear
couples ion-acoustic waves with ion-cyclotron waves and leads, under favorable
conditions, to their efficient reciprocal transformations. It is shown that in
a two-dimensional setup this coupling has a remarkable feature: it is governed
by equations that are exactly similar to the ones describing coupling of sound
waves with internal gravity waves [Rogava & Mahajan: Phys. Rev. E vol.55, 1185
(1997)] in neutral fluid flows. Using another noteworthy quantum mechanical
analogy we calculate transformation coefficients and give fully analytic,
quantitative description of the coupling efficiency for flows with low shearing
rates.Comment: 5 pages, no figures. Submitted to "Physics of Plasmas
Complex Dynamics of Correlated Electrons in Molecular Double Ionization by an Ultrashort Intense Laser Pulse
With a semiclassical quasi-static model we achieve an insight into the
complex dynamics of two correlated electrons under the combined influence of a
two-center Coulomb potential and an intense laser field. The model calculation
is able to reproduce experimental data of nitrogen molecules for a wide range
of laser intensities from tunnelling to over-the-barrier regime, and predicts a
significant alignment effect on the ratio of double over single ion yield. The
classical trajectory analysis allows to unveil sub-cycle molecular double
ionization dynamics.Comment: 5 pages, 5 figures. to appear in Phys. Rev. Lett.(2007
Spectroscopic Analysis of an EIT Wave/Dimming Observed by Hinode/EIS
EIT waves are a wavelike phenomenon propagating outward from the coronal mass
ejection (CME) source region, with expanding dimmings following behind. We
present a spectroscopic study of an EIT wave/dimming event observed by
Hinode/EIS. Although the identification of the wave front is somewhat affected
by the pre-existing loop structures, the expanding dimming is well defined. We
investigate the line intensity, width, and Doppler velocity for 4 EUV lines. In
addition to the significant blue shift implying plasma outflows in the dimming
region as revealed in previous studies, we find that the widths of all the 4
spectral lines increase at the outer edge of the dimmings. We illustrate that
this feature can be well explained by the field line stretching model, which
claims that EIT waves are apparently moving brightenings that are generated by
the successive stretching of the closed field lines.Comment: 11 pages, 7 figure
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