57,531 research outputs found
Inconsistencies between lifetime and polarizability measurements in Cs
Electric-dipole matrix elements for 6p-nd, n=5, 6, 7 transitions in cesium
are calculated using a relativistic all-order method. The resulting matrix
elements are used to evaluate 5d lifetimes and 6p polarizabilities. The data
are compared with experimental lifetime and polarizability measurements made by
different groups. Domination of the 6p scalar polarizabilities by 5d-6p dipole
matrix elements facilitates an exacting consistency check of 5d lifetime and 6p
polarizability data. Values of 5d-6p matrix elements obtained from experimental
5d lifetime data are found to be inconsistent with those inferred from 6p
polarizabilities derived from experimental Stark shift data. Our ab initio
calculated 6p polarizabilities agree well with experimental determinations.Comment: 5 pages, submitted to Physical Review
The massive binary population of the starburst cluster Westerlund 1
We present initial results from a long-baseline radial velocity survey for massive binaries in the cluster Westerlund 1. Four systems are examined: the dust-producing WC binary W239, the double-lined eclipsing binary W13, and the single-lined B0 supergiants W43a and W3003. Finally, the evolutionary implications for the population of massive stars in Westerlund 1 are discussed
The Akulov-Volkov Lagrangian, Symmetry Currents and Spontaneously Broken Extended Supersymmetry
A generalization of the Akulov-Volkov effective Lagrangian governing the self
interactions of the Nambu-Goldstone fermions associated with spontaneously
broken extended supersymmetry as well as their coupling to matter is presented
and scrutinized. The resulting currents associated with R-symmetry,
supersymmetry and space-time translations are constructed and seen to form a
supermultiplet structure.Comment: 17 pages, LaTeX; Title, abstract and introduction changes, references
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Literature survey of properties of synfuels derived from coal
A literature survey of the properties of synfuels for ground-based gas turbine applications is presented. Four major concepts for converting coal into liquid fuels are described: solvent extraction, catalytic liquefaction, pyrolysis, and indirect liquefaction. Data on full range syncrudes, various distillate cuts, and upgraded products are presented for fuels derived from various processes, including H-coal, synthoil, solvent-refined coal, donor solvent, zinc chloride hydrocracking, co-steam, and flash pyrolysis. Some typical ranges of data for coal-derived low Btu gases are also presented
Magic wavelengths for optical cooling and trapping of lithium
Using first-principles calculations, we identify magic wavelengths for the
2s-2p and 2s-3p transitions in lithium. The ns and np atomic levels have the
same ac Stark shifts at the corresponding magic wavelength, which facilitates
state-insensitive optical cooling and trapping. Tune-out wavelengths for which
the ground-state frequency-dependent polarizability vanishes are also
calculated. Differences of these wavelengths between 6Li and 7Li are reported.
Our approach uses high-precision, relativistic all-order methods in which all
single, double, and partial triple excitations of the Dirac-Fock wave functions
are included to all orders of perturbation theory. Recommended values are
provided for a large number of Li electric-dipole matrix elements. Static
polarizabilities for the 2s, 2p, 3s, 3p, and 3d levels are compared with other
theory and experiment where available. Uncertainties of all recommended values
are estimated. The magic wavelengths for the uv 2s-3p transition are of
particular interest for the production of a quantum gas of lithium [Duarte et
al., Phys. Rev. A 84, 061406R (2011)].Comment: 7 pages, 5 figure
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