Abstract
The description begins with an operator master equation for the atom plus incident field. Reduced atomic matrix elements are derived for arbitrary field strengths. First- and second-order correlation functions in the scattered field are also obtained and discussed in relation to the scattered spectrum and intensity-fluctuation measurements. This formalism has the appealing feature that all information is readily available from the one set of four coupled equations. The deficiencies in both the one-photon approximation and the semiclassical perspective are established in a natural and transparent fashion.