Coherence-enhanced optical determination of the $^{229}$Th isomeric   transition
  The impact of coherent light propagation on the excitation and fluorescence of thorium nuclei in a crystal lattice environment is investigated theoretically. We find that in the forward direction the fluorescence signal exhibits characteristic intensity modulations dominated by an orders of magnitude faster, sped-up initial decay signal. This feature can be exploited for the optical determination of the isomeric transition energy. In order to obtain a unmistakable signature of the isomeric nuclear fluorescence, we put forward a novel scheme for the direct measurement of the transition energy via electromagnetically modified nuclear forward scattering involving two fields that couple three nuclear states. 
Wen-Te Liao, Sumanta Das, Christoph H. Keitel and Adriana P\'alffy
physics.atom-ph cond-mat.other physics.optics