31,630 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
An Evaluation of Herbicides for Broadleaf-Weed Control in Rapeseed: Efficacy, Phytotoxicity, and Soil Persistence Studies
At the recommended rates (1.0 lb/A for trifluralin, ethalfluralin, EL5261; 0.75 lb/A for dinitramine; 1.2 lb/A for nitrofen), none of the herbicides we evaluated in these studies reduced rapeseed stands, yields, or test weights. However, at higher rates (1. 5, 3.0 lb A), dinitramine reduced rapeseed stands, but this did not result in decreased yields. None of the other herbicides reduced rapeseed stand, yield, or test weights when applied at up to four times the recommended rate. No trifluralin residues were detected in rapeseed whole-plant or seed samples. All of the herbicides provided adequate control of common lambsquarters (Chenopodium album L.). Corn spurry (Spergula arvensis L.) was controlled by trifluralin. ethalfluralin. EL-5261, and nitrofen. All of the herbicides except nitrofen controlled chickweed [Stellaria media (L.) Cyrillo].
In 1979, 51 per cent of the trifluralin applied remained at the end of the growing season in one study while 26 per cent remained in another study. The rate of degradation at three sites in 1979 were as follows (greatest to least); Delta Junction, Matanuska Valley, Fairbanks. Degradation rates of trifluralin were not significantly different in three soil types or at two different application rates. Trifluralin showed no signs of leaching through the soil profile. In 1981, 25 per cent of the trifluralin, 8 per cent of the ethalfluralin, and 24 per cent of the EL-5261 applied remained at the end of the growing season. Despite the relatively long persistence of these preplant, incorporated herbicides, yields and test weights of barley planted in succeeding years were not reduced. A benefit of these persistent residues was control of broadleaf weeds in the succeeding barley crop
John Wheeler, relativity, and quantum information
In spring 1952, as John Wheeler neared the end of design work for the first thermonuclear explosion, he plotted a radical change of research direction: from particles and atomic nuclei to general relativity
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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