Philip H. Jones, Onofrio M. Maragò & Giovanni Volpe
Fig. 24.4 — Bose-Einstein condensation
Formation of a Bose–Einstein condensate in a cloud of rubidium atoms. The onset of BEC is detected by imaging the time-of-flight expansion of atomic clouds: the thermal atoms (left) feature an isotropic expansion, while the condensate (right) has an anisotropic profile corresponding to the anisotropic confinement in the magnetic trap. In the three-dimensional images (bottom), the sudden increase in the optical depth (corresponding to an increase of atomic density) as the temperature is reduced can be observed.
Adapted from Maragò, Ph.D. thesis, University of Oxford (2001)