  Expression for the probability of the spontaneous emission of high-order
harmonics when the emitter phases are synchronized and are obtained in the
region where the multiphoton approximation is applicable to the description of
the ionization of an atom (where the adiabaticity parameter satisfies gamma >
1). The dependence of this probability on the main parameters of the pump wave
and the atomic medium is established. Criteria for observing emission are
formulated with the consideration of phase locking.
