Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

Q: Quantenoptik und Photonik

Q 52: Postdeadline

Q 52.8: Vortrag

Donnerstag, 25. März 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 ω_Q and damping rate Γ_Q 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 τ_c⁻¹=√2  n₀v_thσ. We observe the full crossover from the collisionless to the hydrodynamic regime, covering the range 0.02 ∼^< ω_zτ_c ∼^< 5 with ω_z/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 ω_zτ_c is of vital importance because the total crossover-change in frequency is only 29%, with √12/5 ω_z<ω_Q<2 ω_z, and the quadrupole frequency shifts rapidly near the crossover point ( dlogω_Q/dlogτ_c=0.12 ).