RADIATIVE PROPERTIES OF A 2-LEVEL SYSTEM IN THE PRESENCE OF MIRRORS

Using a a first-order approximation in time-dependent perturbation the ory, we evaluate the probability per unit time of spontaneous emission by a two-level system coupled to a Hermitian massless scaler field in the presence of either one or two infinite perfectly reflecting plate s (mirrors). We consider the effects of a finite interaction time betw een the system and the quantized field. Furthermore, using the image m ethod in imaginary time, we study radiative processes at finite temper ature. We show that vacuum and thermal fluctuations give independent c ontributions to the total transition. rate and that both are modified by the presence of the mirrors. In the two-parallel-plate geometry, we find that the position average of the spontaneous emission rate is eq ual to the free-space rate for resonant cavities, but is suppressed in nonresonant cavities.