Unformatted text preview: mples. Spectra we
2p 3 1.5 kHz for free particles. The
taken for trapped condensates at three different densitie
by compressing or decompressing the condensates in th
Figure 3.2: Experimental pulsed on at anof momentum transfer cm2BEC by Bragg
beams were observation intensity of about 1 mW to
for a duration of 400 ms. To as shown in ﬁg 3.1.
sattering. Atoms were exposed to laser beamssuppress super-radiant Time of ﬂight prior to the optical excitation.
Rayleigh scattering , both beams real linearly polartechnique converts momentum occupations into were space images. Figure taken resonance for the expanded cloud was ce
tered at 1.54(15) kHz with an rms width of 900 Hz co
ized in the plane deﬁned by the condensate axis and the
from Ref. .
sistent with Doppler broadening . This frequenc
wave vector of the light.
includes an expected 160 Hz residual mean-ﬁeld shif
The Bragg scattering of a trapped condensate was analyzed by switching off the magnetic trap 100 ms after the
end of the light pulse, and allowing the cloud to freely
evolve for 70 ms. During the free expansion, the density of the atomic cloud dropped and quasiparticles in the
condensate transformed into free particles and we...
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- Fall '10
- Physics, Bose-Einstein condensation, Bogoliubov Theory, Bogoliubov quasiparticles