Modelling the interaction of hot atoms with strong electromagnetic fields

Summary form only given. The prediction of a longitudinal instability breaking the translational symmetry in an atomic sample in interaction with an intense electromagnetic field has attracted considerable interest. Indeed, the appearance of a macroscopic organization of the individual atoms mediated by the electromagnetic field is a phenomenon which, if truly observed, is of great relevance in the field of the radiation-matter interaction. The experimental observations performed so far have provided some indirect evidence for the possible existence of such a phenomenon, but it has not been possible to perform a close comparison with theoretical predictions because of the severe approximations involved in the modellization. Since experiments can be most easily conducted in cells, i.e., on samples that are in thermodynamical equilibrium with their oven ("hot" atoms), we have decided to modify the model to account for stochastic collisions with the atoms of the buffer gas that thus acts as a thermostat.