Relaxation via spontaneous emission of bosons: Non-Markovian approach

An isomorphism is established between the configurational interaction of one discrete level with a continuum, and a relaxation via spontaneous emission of bosons in one-boson approximation. Conditions of one-boson approximation are derived. This approach enables one to overcome limitations of the Markovian or Weisskopf-Wigner approximations. The results qualitatively differ from those obtained in the master-equation approach. In a general case, the probability to remain in an excited state has asymptotically oscillatory behavior, unlike in the Weisskopf-Wigner approximation in which it tends to zero.