EMISSION OF GAMMA-RAYS BY ELECTRON-NUCLEAR DOUBLE TRANSITIONS

In this paper we discuss the relevance of electron-nuclear double tran sitions for the problem of the amplification of gamma rays. We conside r the electron-nuclear coupled system of Eu-151 in a CaF2 lattice, in the presence of a strong static magnetic field. We analyze the possibi lity of pumping this electron-nuclear coupled system from the ground a tomic electron Zeeman level to a higher electron level with the aid of a microwave magnetic field, while the nucleus is simultaneously under going a gamma-ray transition to the nuclear ground state. It is shown that an overall inversion condition can be satisfied even in the absen ce of inversion of the nuclear populations, provided that the ratio of the electron populations in the excited and ground electron Zeeman st ates has a sufficiently small value.