Internal state conversion of ultracold gases
Résumé
We consider an ultracold gas of (non-condensed) bosons or fermions with twointernal states, and study the effect of a gradient of the transitionfrequency between these states. When a $\\\\pi/2$ RF pulse is applied to thesample, exchange effects during collisions transfer the atoms into internal stateswhich depend on the direction of their velocity. This results, after a shorttime, in a spatial separation between the two states. A kinetic equation issolved analytically and numerically; the results agree well with the recentobservations of Lewandowski et al.