SIMBAD references

In this paper we consider a general problem of astrophysical lasers operating with optical pumping by accidental resonance (PAR) with strong spontaneous emission lines of other elements. The origin of population inversion and the coefficient of amplification due to the optical excitation of atoms (ions) by a four-level scheme with PAR are analyzed. We elucidate conclusively the question of the manifestation of astrophysical lasers in the optical region of the spectrum, which in principle differs from that of astrophysical masers in the microwave range.