103 research outputs found
Calculation of atomic spontaneous emission rate in 1D finite photonic crystal with defects
We derive the expression for spontaneous emission rate in finite
one-dimensional photonic crystal with arbitrary defects using the effective
resonator model to describe electromagnetic field distributions in the
structure. We obtain explicit formulas for contributions of different types of
modes, i.e. radiation, substrate and guided modes. Formal calculations are
illustrated with a few numerical examples, which demonstrate that the
application of effective resonator model simplifies interpretation of results.Comment: Cent. Eur. J. Phys, in pres
Cooperative spontaneous emission in nonuniform media
The subject of this paper is modification of cooperative spontaneous emission
by a nonuniform medium, with nonuniform distributions of electromagnetic field.
A brief analyzis is presented and it is postulated, that if spontaneous
emission from an atom is strongly suppressed, cooperative emission with another
atom may be a preferred emission channel and counteract the suppression.Comment: The final publication is available at http://www.epj.or
Effects of Substituents on the Length of Central C(sp^3)-C(sp^3) Bond in Anthracene Photodimers and Related Molecules
Effects of substituents on the lengths of the central CâC single bond in the butterfly-shaped anthracene photodimers (1)â(7) and lepidopterenes (8) are studied. X-Ray analysis of the photodimer (10) of 9,10-difluoroanthracene gave a C(9)âC(10âČ) bond length of 1.631 (3)Ă
. An attempt to re-determine molecular structure of the photoisomer (5) of [2.2](9,10) anthracenophane (12) by neutron diffraction analysis is also reported [C(9)âC(10âČ): obs. 1.64(1), calc. 1.63(1)Ă
]. The D_2 structure that had been proposed for the minimum-energy conformation of (5) is questioned and the D_(2h) symmetric conformation is suggested on the basis of the diffraction results and MNDO calculations. The experimentally determined distances of the long central CâC bonds in these butterfly compounds including dianthronyl (9) are well reproduced by MNDO calculations with a standard deviation of 0.013 Ă
. Small but significant further elongation of the central CâC bond by up to 0.07 Ă
resulting from annulation of cyclobutane or cyclopentane ring in anthracene photodimers and from remote chlorine substitution in lepidopterene are interpreted in terms of the increased ÏâÏ^* orbital interaction
Transient heat generation in a quantum dot under a step-like pulse bias
We study the transient heat generation in a quantum dot system driven by a
step-like or a square-shaped pulse bias. We find that a periodically
oscillating heat generation arises after adding the sudden bias. One
particularly surprising result is that there exists a heat absorption from the
zero-temperature phonon subsystem. Thus the phonon population in
non-equilibrium can be less than that of the equilibrium electron-phonon
system. In addition, we also ascertain the optimal conditions for the operation
of a quantum dot with the minimum heat generation.Comment: 6 pages, 4 figure
Spintronic transport and Kondo effect in quantum dots
We investigate the spin-dependent transport properties of quantum-dot based
structures where Kondo correlations dominate the electronic dynamics. The
coupling to ferromagnetic leads with parallel magnetizations is known to give
rise to nontrivial effects in the local density of states of a single quantum
dot. We show that this influence strongly depends on whether charge
fluctuations are present or absent in the dot. This result is confirmed with
numerical renormalization group calculations and perturbation theory in the
on-site interaction. In the Fermi-liquid fixed point, we determine the
correlations of the electric current at zero temperature (shot noise) and
demonstrate that the Fano factor is suppressed below the Poissonian limit for
the symmetric point of the Anderson Hamiltonian even for nonzero lead
magnetizations. We discuss possible avenues of future research in this field:
coupling to the low energy excitations of the ferromagnets (magnons), extension
to double quantum dot systems with interdot antiferromagnetic interaction and
effect of spin-polarized currents on higher symmetry Kondo states such as
SU(4).Comment: 11 pages, 5 figures. Proceedings of the 3rd Intl. Conf. on Physics
and Applications of Spin-Related Phenomena in Semiconductors, Santa Barbara,
200
History and current research in the field of radiochemistry at Maria Curie-SkĆodowska University
Extending the double difference location techniqueâimproving hypocenter depth determination
Investigation of chemical transformations of thiophenylglycoside of muramyl dipeptide on the fumed silica surface using TPD-MS, FTIR spectroscopy and ES IT MS
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