Loading of a Bose-Einstein condensate in the boson accumulation regime

We study the optical loading of a trapped Bose-Einstein condensate by spontaneous emission of atoms in excited electronic state in the boson accumulation regime. We generalize the previous simplified analysis of Cirac and Lewenstein (Phys. Rev. A, 53 (1996) 2466), to a 3D case in which more than one trap level of the excited-state trap is considered. By solving the corresponding quantum many-body master equation, we demonstrate that also for this general situation the photon reabsorption can help to increase the condensate fraction. Such effect could be employed to realize a continuous atom laser, and to overcome condensate losses