Simulated motion
Figure 4. A simulation of an atom's motion in a cavity. The relatively small coupling between the atom and the light field in the larger cavity in the MPQ experiment increases the role of the momentum kicks from spontaneous emission events. These kicks perturb the otherwise regular motion of the atom in a plane perpendicular to the cavity axis and make the atomic trajectory (yellow) more random. The atom enters from below and is trapped for about 1.2 ms.