We study the effect of electromagnetic radiation on the condensate of a Bose
gas. In an earlier paper we considered the problem for two simple models
showing the cooperative effect between Bose-Einstein condensation and
superradiance. In this paper we formalise the model suggested by Ketterle et al
in which the Bose condensate particles have a two level structure. We present a
soluble microscopic Dicke type model describing a thermodynamically stable
system. We find the equilibrium states of the system and compute the
thermodynamic functions giving explicit formulae expressing the cooperative
effect between Bose-Einstein condensation and superradiance