Single molecule in a Bose-Einstein condensate

We study a model describing a rotating linear rigid molecule interacting wi th a Bose-Einstein condensate. A generalization of the Landau criterion is established and gives the limit for which the molecule moves translationall y and rotationally into the condensate without any friction. In particular, we show that the rotational energy released by the molecule is large enoug h to eject one atom out of the condensate. The detection of such an atom pr ovides a direct measurement of the low-energy cross section of the scatteri ng with the rotating molecule, Finally, increases of inertia and of centrif ugal distortion of the molecule due to the surrounding condensate are estim ated and compared with the experimental data obtained for a He-4 droplet.