Gamma lasers and stellar atmospheres

The development of a gamma laser based on long lived isomeric nuclei is proved to be exclusively practical problem. Einstein's analysis of a quantum system transition between two descrete levels is shown to refer transitions from any excited to the ground state of the system. Relation between Einstein's coefficients for transitions among two excited states is further obtained. The integral cross section for absorption and stimulated emission in a transition between two excited states are calculated for different sources. Using these results the concentration of the isomer states necessary for amplification is obtained. Its value for the specific nuclide 125mTe at helium temperature is N0=8x1020 cm-3 which is 30 times less than the maximum possible concentration of the 125Te nuclei. The influence of the corrections in the cross section expressions over the spectrum of a homogeneous gas in a thermodynamic equilibrium, as the case of stellar atmosphere, is shown. 3 figs., 9 refs