4,322 research outputs found
Phase Transition in a One-Dimensional Extended Peierls-Hubbard Model with a Pulse of Oscillating Electric Field: II. Linear Behavior in Neutral-to-Ionic Transition
Dynamics of charge density and lattice displacements after the neutral phase
is photoexcited is studied by solving the time-dependent Schr\"odinger equation
for a one-dimensional extended Peierls-Hubbard model with alternating
potentials. In contrast to the ionic-to-neutral transition studied previously,
the neutral-to-ionic transition proceeds in an uncooperative manner as far as
the one-dimensional system is concerned. The final ionicity is a linear
function of the increment of the total energy. After the electric field is
turned off, the electronic state does not significantly change, roughly keeping
the ionicity, even if the transition is not completed, because the ionic
domains never proliferate. As a consequence, an electric field with frequency
just at the linear absorption peak causes the neutral-to-ionic transition the
most efficiently. These findings are consistent with the recent experiments on
the mixed-stack organic charge-transfer complex, TTF-CA. We artificially modify
or remove the electron-lattice coupling to discuss the origin of such
differences between the two transitions.Comment: 17 pages, 9 figure
Photoinduced magnetic bound state in itinerant correlated electron system with spin-state degree of freedom
Photo-excited state in correlated electron system with spin-state degree of
freedom is studied. We start from the two-orbital extended Hubbard model where
energy difference between the two orbitals is introduced. Photo-excited
metastable state is examined based on the effective model Hamiltonian derived
by the two-orbital Hubbard model. Spin-state change is induced by
photo-irradiation in the low-spin band insulator near the phase boundary.
High-spin state is stabilized by creating a ferromagnetic bound state with
photo-doped hole carriers. An optical absorption occurs between the bonding and
antibonding orbitals inside of the bound state. Time-evolution for
photo-excited states is simulated in the time-dependent mean-field scheme.
Pair-annihilations of the photo-doped electron and hole generate the high-spin
state in a low-spin band insulator. We propose that this process is directly
observed by the time-resolved photoemission experiments.Comment: 15 pages, 16 figure
First ALMA Observation of a Solar Plasmoid Ejection from an X-ray Bright Point
Eruptive phenomena such as plasmoid ejections or jets are an important
feature of solar activity with the potential for improving our understanding of
the dynamics of the solar atmosphere. Such ejections are often thought to be
signatures of the outflows expected in regions of fast magnetic reconnection.
The 304 A EUV line of Helium, formed at around 10^5 K, is found to be a
reliable tracer of such phenomena, but the determination of physical parameters
from such observations is not straightforward. We have observed a plasmoid
ejection from an X-ray bright point simultaneously at millimeter wavelengths
with ALMA, at EUV wavelengths with AIA, in soft X-rays with Hinode/XRT. This
paper reports the physical parameters of the plasmoid obtained by combining the
radio, EUV and X-ray data. As a result, we conclude that the plasmoid can
consist either of (approximately) isothermal 10^5 K plasma that is optically
thin at 100 GHz, or else a 10^4 K core with a hot envelope. The analysis
demonstrates the value of the additional temperature and density constraints
that ALMA provides, and future science observations with ALMA will be able to
match the spatial resolution of space-borne and other high-resolution
telescopes.Comment: 10 page, 5 figures, accepted for publication in Astrophysical Journal
Letter. The movie can be seen at the following link:
http://hinode.nao.ac.jp/user/shimojo/data_area/plasmoid/movie5.mp
Phase Transition in a One-Dimensional Extended Peierls-Hubbard Model with a Pulse of Oscillating Electric Field: III. Interference Caused by a Double Pulse
In order to study consequences of the differences between the
ionic-to-neutral and neutral-to-ionic transitions in the one-dimensional
extended Peierls-Hubbard model with alternating potentials for the TTF-CA
complex, we introduce a double pulse of oscillating electric field in the
time-dependent Schr\"odinger equation and vary the interval between the two
pulses as well as their strengths. When the dimerized ionic phase is
photoexcited, the interference effect is clearly observed owing to the
coherence of charge density and lattice displacements. Namely, the two pulses
constructively interfere with each other if the interval is a multiple of the
period of the optical lattice vibration, while they destructively interfere if
the interval is a half-odd integer times the period, in the processes toward
the neutral phase. The interference is strong especially when the pulse is
strong and short because the coherence is also strong. Meanwhile, when the
neutral phase is photoexcited, the interference effect is almost invisible or
weakly observed when the pulse is weak. The photoinduced lattice oscillations
are incoherent due to random phases. The strength of the interference caused by
a double pulse is a key quantity to distinguish the two transitions and to
evaluate the coherence of charge density and lattice displacements.Comment: 16 pages, 8 figure
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Vibronic mixing enables ultrafast energy flow in light-harvesting complex II.
Since the discovery of quantum beats in the two-dimensional electronic spectra of photosynthetic pigment-protein complexes over a decade ago, the origin and mechanistic function of these beats in photosynthetic light-harvesting has been extensively debated. The current consensus is that these long-lived oscillatory features likely result from electronic-vibrational mixing, however, it remains uncertain if such mixing significantly influences energy transport. Here, we examine the interplay between the electronic and nuclear degrees of freedom (DoF) during the excitation energy transfer (EET) dynamics of light-harvesting complex II (LHCII) with two-dimensional electronic-vibrational spectroscopy. Particularly, we show the involvement of the nuclear DoF during EET through the participation of higher-lying vibronic chlorophyll states and assign observed oscillatory features to specific EET pathways, demonstrating a significant step in mapping evolution from energy to physical space. These frequencies correspond to known vibrational modes of chlorophyll, suggesting that electronic-vibrational mixing facilitates rapid EET over moderately size energy gaps
Reduction of quantum systems on Riemannian manifolds with symmetry and application to molecular mechanics
This paper deals with a general method for the reduction of quantum systems
with symmetry. For a Riemannian manifold M admitting a compact Lie group G as
an isometry group, the quotient space Q = M/G is not a smooth manifold in
general but stratified into a collection of smooth manifolds of various
dimensions. If the action of the compact group G is free, M is made into a
principal fiber bundle with structure group G. In this case, reduced quantum
systems are set up as quantum systems on the associated vector bundles over Q =
M/G. This idea of reduction fails, if the action of G on M is not free.
However, the Peter-Weyl theorem works well for reducing quantum systems on M.
When applied to the space of wave functions on M, the Peter-Weyl theorem
provides the decomposition of the space of wave functions into spaces of
equivariant functions on M, which are interpreted as Hilbert spaces for reduced
quantum systems on Q. The concept of connection on a principal fiber bundle is
generalized to be defined well on the stratified manifold M. Then the reduced
Laplacian is well defined as a self-adjoint operator with the boundary
conditions on singular sets of lower dimensions. Application to quantum
molecular mechanics is also discussed in detail. In fact, the reduction of
quantum systems studied in this paper stems from molecular mechanics. If one
wishes to consider the molecule which is allowed to lie in a line when it is in
motion, the reduction method presented in this paper works well.Comment: 33 pages, no figure
Mechanism for Localization of Pheophorbides in Tumor. I. Biodistribution and Subcellular Distribution of 14C-Labeled Pheophorbide and Chlorin in Tumor-Bearing Mice
開始ページ、終了ページ: 冊子体のページ付
Daidzein and genistein but not their glucosides are absorbed from the rat stomach
AbstractAbsorption of isoflavone aglycones and glucosides was compared in rats. Daidzein, genistein, daidzin and genistin were orally administered at a dose of 7.9 μmol/kg in 25 mM Na2CO3 and next their metabolite concentration in blood plasma was monitored for 30 min. After isoflavone glucosides administration, their metabolites appeared in plasma with a few minutes delay as compared to aglycones, which suggested that aglycones, but not glucosides, were absorbed already in the rat stomach. This observation was confirmed when absorption site was restricted solely to the stomach and absorption was shown to be independent of the vehicle pH used for administration
How to relate the oscillator and Coulomb systems on spheres and pseudospheres?
We show that the oscillators on a sphere and pseudosphere are related, by the
so-called Bohlin transformation, with the Coulomb systems on the pseudosphere:
the even states of an oscillator yields the conventional Coulomb system on
pseudosphere, while the odd states yield the Coulomb system on pseudosphere in
the presence of magnetic flux tube generating half spin. In the higher
dimensions the oscillator and Coulomb(-like) systems are connected in the
similar way. In particular, applying the Kustaanheimo-Stiefel transformation to
the oscillators on sphere and pseudosphere, we obtained the preudospherical
generalization of MIC-Kepler problem describing three-dimensional charge-dyon
system.Comment: 12 pages, Based on talk given at XXIII Colloquium on Group
Theoretical Methods in Physics (July 31-August 5, 2000, Dubna
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