Physical Review A
Spectrum of cascade spontaneous emission: General theory including systems with close transition frequencies
Alexander A. Makarov, Vladimir I. Yudson
Abstract
The process of a cascade light emission by an excited multilevel quantum system has been described exactly. A multiphoton wave function of the system at an arbitrary time has been derived, which allows one to find any characteristic of the emitted field. Using this wave function, we have obtained a general expression for the cascade emission spectrum. This expression is of special interest when some transitions have close frequencies; this case has not been treated before. We present several examples of application of the obtained general expression.