6,293 research outputs found
Low-temperature quenching of one-dimensional localised Frenkel excitons
We present a theoretical analysis of low-temperature quenching of
one-dimensional Frenkel excitons that are localised by moderate on-site
(diagonal) uncorrelated disorder. Exciton diffusion is considered as an
incoherent hopping over localization segments and is probed by the exciton
fluorescence quenching at point traps. The rate equation is used to calculate
the temperature dependence of the exciton quenching. The activation temperature
of the diffusion is found to be of the order of the width of the exciton
absorption band. We demonstrate that the intra-segment scattering is extremely
important for the exciton diffusion. We discuss also experimental data on the
fast exciton-exciton annihilation in linear molecular aggregates at low
temperatures.Comment: 7 pages, 3 figures, accepted to Chem. Phys. Let
Local level statistics for optical and transport properties of disordered systems at finite temperature
It is argued that the (traditional) global level statistics which determines
localization and coherent transport properties of disordered systems at zero
temperature (e.g. the Anderson model) becomes inappropriate when it comes to
incoherent transport. We define local level statistics which proves to be
relevant for finite temperature incoherent transport and optics of
one-dimensional systems (e.g. molecular aggregates, conjugated polymers, etc.).Comment: 4 pages, 2 figures, reported at EXCON'2006, to appear in the physica
status solidi (c
Optical bistability and hysteresis of hybrid metal-semiconductor nano-dimer
Optical response of an artificial composite nano-dimer comprising a
semiconductor quantum dot and a metal nanosphere is analyzed theoretically. We
show that internal degrees of freedom of the system can manifest bistability
and optical hysteresis as functions of the incident field intensity. We argue
that these effects can be observed for the real world systems, such as a CdSe
quantum dot and an Au nanoparticle hybrids. These properties can be revealed by
measuring the optical hysteresis of the Rayleigh scattering. We show also that
the total dipole moment of the system can be switched abruptly between its two
stable states by small changes in the excitation intensity. The latter promises
various applications in the field of all-optical processing at nanoscale, the
most underlying of them being the volatile optical memory.Comment: 6 two column pages, 5 figures, to appear in Phys. Rev.
Fermi Bubbles: an Elephant in the Gamma-ray Sky
The Fermi bubbles are one of the most remarkable features in the gamma-ray
sky revealed by the Fermi Large Area Telescope (LAT). The nature of the
gamma-ray emission and the origin of the bubbles are still open questions. In
this note, we will review some basic features of leptonic and hadronic modes of
gamma-ray production. At the moment, gamma rays are our best method to study
the bubbles, but in order to resolve the origin of the bubbles multi-wavelength
and multi-messenger observations will be crucial.Comment: Published in proceedings for RICAP16 conferenc
Selection of dominant multi-exciton transitions in disordered linear J-aggregates
We show that the third-order optical response of disordered linear
J-aggregates can be calculated by considering only a limited number of
transitions between (multi-) exciton states. We calculate the pump-probe
absorption spectrum resulting from the truncated set of transitions and show
that, apart from the blue wing of the induced absorption peak, it agrees well
with the exact spectrum.Comment: 8 pages, 2 figures, accepted to Journal of Luminescenc
Galactic center gamma-ray excess and the Fermi bubbles
Galactic center (GC) is expected to be the brightest source of possible dark
matter (DM) annihilation signal. Excess gamma-ray emission has been detected by
several groups. Both DM and more conventional astrophysical explanations of the
excess have been proposed. In this report, we discuss possible effects of
modeling the Fermi bubbles at low latitudes on the GC excess. We consider a
template of the Fermi bubbles at low latitudes derived by assuming that the
spectrum between 1 GeV and 10 GeV at low latitudes is the same as at high
latitudes. We argue that the presence of the Fermi bubbles near the GC may have
a significant influence on the spectrum of the GC excess, especially at
energies above 10 GeV.Comment: Proceedings of LaThuile 2017 conferenc
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