Collective Oscillations of Two Colliding Bose-Einstein Condensates

Two ${}^{87}\mathrm{Rb}$ condensates ( $F=2\mathrm{}$, $m_f=2\mathrm{}$, and $m_f=1\mathrm{}$) are produced in highly displaced harmonic traps and the collective dynamical behavior is investigated. The mutual interaction between the two condensates is evidenced in the center-of-mass oscillations as a frequency shift of $6.4\left(3\right)\%$. Calculations based on a mean-field theory well describe the observed effects of periodical collisions both on the center-of-mass motion and on the shape oscillations.