‘Two-level’, Stokes, and anti-Stokes pumping of a nuclear gamma laser with anisotropic hidden inversion

Recoil in radiative gamma transitions leads to a discrete line spectrum of absorption and emission resonances in an ensemble of free nuclei. This opens up the possibility of efficient pumping of such nuclei and of hidden inversion in an nonstandard ‘optical’ scheme without participation of the third auxiliary level, as well as in Stokes and anti-Stokes schemes. Quantitative estimates are given for several nuclides.