  In this paper we conjecture that some specific properties of an electroactive
region of thunderclouds play the major role in an initiation of a lightning
flash. The electroactive region is modeled here as a quantum two-level system
of oxygen molecules which are assumed to have two (ground and excited) states,
where transitions from ground to excited states come as a result of
micro-discharges between ice particles. In this case lightning flash
corresponds to the pulse of collective spontaneous radiation caused by the
deexcitations of excited oxygen molecules from metastable state into ground
state.
