The decay of quantum system translated into the excited state depends on the manner of excitation and the system parametres as well [1]. In this case when the system was let to itself after the excitation its next development may be two-fold under the influence of spontaneous transitions of particles from the excited state to the ground state. The first one is the uncoherent spontaneous radiation. In this case all particles of the system are independently radiating. The total power of this radiation is the sum of spontaneous radiation powers of isolated particles. The second case is the coherent radiation, i.e. the particles are radiating into the coherence volume νωh= (c·T′2)3with a single phase (C is the field velocity in the medium andT′2is the phase relaxation time of the system). In the latter case the amplitude of the radiated field is propotional to the particle number N and the power is propotional to the square of particle number. However the second case is realized under the specified conditions only (such as the excitation pulse duration should be shorter than the phase relaxation times of the system and others). In this case the excited system let to itself these specific conditions may be realized (after a characteristic time). Under such conditions the probability W (W ∝N2) of the radiation of the one quantum of field by means of all excited particles is more than the probability of radiation of the one field quantum by means of the one particle. After that the whole system is transferred into the state from which it cannot get out (i.e. superradiant one [2]). In this state the probability of radiation process with the radiation power propotional to the square of particle number is more than anything other. However a two-fold development of the system may takes place. The first way is the free induction type process. And the second one is the avalanche process when the process of radiation proper is preparing the next states of the system and the radiation power is continiously increasing. Here we see the narrowing of the radiation spectrum and shortening of the radiation time in the last case [3]. As a rule the avalanche processes are formed when the excited state of the system is characterized by a certain degree of inversion.