Field and phenomenological description of absorption of particles
  The complicated processes in the medium (decays, reactions and $n\bar{n}$ conversion) involving final state absorption are considered. The calculations in the framework of field and phenomenological approaches are compared. The reasons for disagreement are studied. The field approach can tend to increase of total process probability as well as probability of channel corresponding to absorption, in comparison with phenomenological model. 
V.I.Nazaruk