  The effect of microwave radiation on the resonance fluorescence of a cloud of
cold $^{85}Rb$ atoms in a magnetooptical trap is studied. The radiation
frequency was tuned near the hyperfine splitting frequency of rubidium atoms in
the 5S ground state. The microwave field induced magnetic dipole transitions
between the magnetic sublevels of the 5S(F=2) and 5S(F=3) states, resulting in
a change in the fluorescence signal. The resonance fluorescence spectra were
recorded by tuning the microwave radiation frequency. The observed spectra were
found to be substantially dependent on the transition under study and the
frequency of a repump laser used in the cooling scheme.
