  The photoluminescence (PL) of a two-dimensional electron gas (2DEG) in a high
magnetic field is studied as a function of the filling factor and the
separation d between the electron layer and the valence hole. Depending on the
magnitude of d relative to the magnetic length lambda, two distinct regimes in
the response of the 2DEG to the valence hole occur, with different elementary
emission processes contributing to the PL spectrum. At d<lambda ("strong
coupling" regime), the hole binds one or two electrons to form an exciton (X)
or one of three possible charged exciton (X-) states, a spin-singlet or one of
two spin-triplets. At d>lambda ("weak coupling" regime), the hole decouples or
binds one or two Laughlin quasielectrons to form fractionally charged excitons
(FCX's). The binding energies as well as the emission energies and intensities
of all X- and FCX states are calculated.
