The coupling of an atom to its environment can be strongly dependent on frequency when that atom is placed in, for example, a cavity. We consider here the exact dynamics of a three-level atom for a resonant form of the atom-environment coupling of the type found in a cavity. The three-level atom forms a quantum-beat V system in the general model that we consider. Without the use of perturbation theory, we derive a set of three coupled differential equations that describe the system. Results are compared to quantum beats in free space and an interpretation is provided in terms of the coupling of the three-level system to a pseudomode. The pseudomode is defined by the differential equations involving its amplitude and possesses the properties of a finite-Q cavity mode. The signal from a detector is formulated in terms of a resonant coupling between the detector and the cavity modes. Limits for a broadband and a narrow-band detector are considered. © 1996 The American Physical Society.

• Received 3 May 1996

DOI:https://doi.org/10.1103/PhysRevA.54.3592