In this effect, nuclei in a crystalline solid do not recoil when emitting gamma rays, instead giving all the energy to the photon, which thus has a sharply defined wavelength.  
Work on the resonance absorption of gamma radiation and the discovery of his eponymous effect led to a Nobel Prize. In this effect, nuclei in a crystalline solid do not recoil when emitting gamma rays, instead giving all the energy to the photon, which thus has a sharply defined wavelength.  For ten points, identify this German physicist, winner of a Nobel Prize in 1961.
Work on the resonance absorption of gamma radiation and the discovery of his eponymous effect led to a Nobel Prize.
Rudolf Ludwig Mossbauer