10,995 research outputs found
Quantum Effects in Matter-Wave Diffraction
Advances in micro-technology of the last years have made it possible to carry
optics textbooks experiments over to atomic and molecular beams, such as
diffraction by a double slit or transmission grating. The usual wave-optical
approach gives a good qualitative description of these experiments. However,
small deviations therefrom and sophisticated quantum mechanics yield new
surprising insights on the size of particles and on their interaction with
surfaces.Comment: 6 pages, 3 Postscript figures. To appear in the Proceedings of
Quantum Theory and Symmetry, Cracow, July 2001, edited by E. Kapuscik and A.
Horzela, World Scientifi
Simplified approach to double jumps for fluorescing dipole-dipole interacting atoms
A simplified scheme for the investigation of cooperative effects in the
quantum jump statistics of small numbers of fluorescing atoms and ions in a
trap is presented. It allows the analytic treatment of three dipole-dipole
interacting four-level systems which model the relevant level scheme of Ba+
ions. For the latter, a huge rate of double and triple jumps was reported in a
former experiment and the huge rate was attributed to the dipole-dipole
interaction. Our theoretical results show that the effect of the dipole-dipole
interaction on these rates is at most 5% and that for the parameter values of
the experiment there is practically no effect. Consequently it seems that the
dipole-dipole interaction can be ruled out as a possible explanation for the
huge rates reported in the experiment.Comment: 7 pages, 6 figures, typos corrected, to appear in EPJ D (as highlight
paper
Chemodynamical history of the Galactic Bulge
The Galactic Bulge can uniquely be studied from large samples of individual
stars, and is therefore of prime importance for understanding the stellar
population structure of bulges in general. Here the observational evidence on
the kinematics, chemical composition, and ages of Bulge stellar populations
based on photometric and spectroscopic data is reviewed. The bulk of Bulge
stars are old and span a metallicity range -1.5<~[Fe/H]<~+0.5. Stellar
populations and chemical properties suggest a star formation timescale below ~2
Gyr. The overall Bulge is barred and follows cylindrical rotation, and the more
metal-rich stars trace a Box/Peanut (B/P) structure. Dynamical models
demonstrate the different spatial and orbital distributions of metal-rich and
metal-poor stars. We discuss current Bulge formation scenarios based on
dynamical, chemical, chemodynamical and cosmological models. Despite impressive
progress we do not yet have a successful fully self-consistent chemodynamical
Bulge model in the cosmological framework, and we will also need more extensive
chrono-chemical-kinematic 3D map of stars to better constrain such models.Comment: 9 figures, 55 pages final version to appear in the Annual Reviews of
Astronomy & Astrophysics, volume 5
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