Role of mechanical effects on the excitation spectra of microwave-dressed Rydberg states in a cold atomic cloud

We explore the excitation spectra of cold 87Rb atoms to the 55D_3/2 Rydberg state in the presence of microwave (MW) radiation as a function of MW frequency. The spectra reveal several features around the transition-frequencies between adjacent Rydberg states. We argue that some of these features are indicative of variations in the Rydberg excitation probability while others result from the removal of atoms from the cold cloud as a consequence of a MW induced strong dipole-dipole inter-atomic force. Our claim is supported by experimental observations and theoretical modeling.