München 2004 – scientific programme
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Q: Quantenoptik und Photonik
Q 52: Postdeadline
Q 52.8: Talk
Thursday, March 25, 2004, 21:10–21:20, HS 225
Damping and frequency shifts of collective modes in thermal clouds of 87Rb — •Christian Buggle, Wolf von Klitzing, and Jook T.M. Walraven — FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam
We have studied the frequency ωQ and damping rate ΓQ of the m=0 quadrupole-monopole shape oscillation in thermal clouds of 87Rb confined in an elongated harmonic trap as a function of the central elastic collision rate τc−1=√2 n0vthσ. We observe the full crossover from the collisionless to the hydrodynamic regime, covering the range 0.02 ∼< ωzτc ∼< 5 with ωz/2π the axial trap frequency. We find good agreement with the predictions of the kinetic theory for collective oscillations in harmonic traps. The measurements were done with both phase contrast imaging and absorption imaging. Accurate control over ωzτc is of vital importance because the total crossover-change in frequency is only 29%, with √12/5 ωz<ωQ<2 ωz, and the quadrupole frequency shifts rapidly near the crossover point ( dlogωQ/dlogτc=0.12 ).