Recoil Effects in Microwave Atomic Frequency Standards:. AN Update

We investigate theoretically and by numerical simulations the effects of the atomic recoil on the frequency and fringe contrast of microwave atomic frequency standards. Such effects arise because of the influence of external degrees of freedom on the phases and the spatial positions of the interfering wave packets. We show under which conditions such effects lead to a frequency shift and examine the loss of contrast of the interference signal (Ramsey fringes). Because of limited space this short communication is only an update of a previous more complete paper [1] (henceforth referred to as P1) pointing out the advances and changes since June 2001. We recommend the reader to consult that paper for a more detailed account of the theory.