12,509 research outputs found
In Search of International Evidence: A Lawyer\u27s Guide through the United States Department of Justice
In Search of International Evidence: A Lawyer\u27s Guide through the United States Department of Justice
Trapping of ultracold polar molecules with a Thin Wire Electrostatic Trap
We describe the realization of a dc electric-field trap for ultracold polar
molecules, the thin-wire electrostatic trap (TWIST). The thin wires that form
the electrodes of the TWIST allow us to superimpose the trap onto a
magneto-optical trap (MOT). In our experiment, ultracold polar NaCs molecules
in their electronic ground state are created in the MOT via photoassociation,
achieving a continuous accumulation in the TWIST of molecules in low-field
seeking states. Initial measurements show that the TWIST trap lifetime is
limited only by the background pressure in the chamber.Comment: 4 pages, 3 figure
The non-uniform, dynamic atmosphere of Betelgeuse observed at mid-infrared wavelengths
We present an interferometric study of the continuum surface of the red
supergiant star Betelgeuse at 11.15 microns wavelength, using data obtained
with the Berkeley Infrared Spatial Interferometer each year between 2006 and
2010. These data allow an investigation of an optically thick layer within 1.4
stellar radii of the photosphere. The layer has an optical depth of ~1 at 11.15
microns, and varies in temperature between 1900 K and 2800 K and in outer
radius between 1.16 and 1.36 stellar radii. Electron-hydrogen atom collisions
contribute significantly to the opacity of the layer. The layer has a
non-uniform intensity distribution that changes between observing epochs. These
results indicate that large-scale surface convective activity strongly
influences the dynamics of the inner atmosphere of Betelgeuse, and mass-loss
processes.Comment: 13 pages, 5 figures, in press (ApJ
Controlling Condensate Collapse and Expansion with an Optical Feshbach Resonance
We demonstrate control of the collapse and expansion of an 88Sr Bose-Einstein
condensate using an optical Feshbach resonance (OFR) near the 1S0-3P1
intercombination transition at 689 nm. Significant changes in dynamics are
caused by modifications of scattering length by up to +- ?10a_bg, where the
background scattering length of 88Sr is a_bg = -2a0 (1a0 = 0.053 nm). Changes
in scattering length are monitored through changes in the size of the
condensate after a time-of-flight measurement. Because the background
scattering length is close to zero, blue detuning of the OFR laser with respect
to a photoassociative resonance leads to increased interaction energy and a
faster condensate expansion, whereas red detuning triggers a collapse of the
condensate. The results are modeled with the time-dependent nonlinear
Gross-Pitaevskii equation.Comment: 5 pages, 3 figure
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