Mössbauer effect[1]refers to the recoilless emission and absorption of nuclear transition photons.When the nuclei are tightly bound inside the lattice,there is chance that photon emission and absorption recoils collectively with the lattice,leading to an extremely tiny photon frequency shift and ultra-high accuracy in the resonant absorption energy.This resonance effect won Rudolf Ludwig Mössbauer the 1961 Nobel Prize,and later developed into the flourishing field of Mössbauer spectroscopy.Shortly after its discovery,Mössbauer resonance quickly found an important role in the early tests of Einstein's theory of general relativity:Photon frequency fluctuation arising from gravitational effects can be revealed by the resonance's outstanding precision.Well-known examples include the 1960–1965 experiment in Jefferson Physical Laboratory[2],which successfully demonstrated a frequency shift due to a 22-meter height difference under the Earth's gravitational field.Other examples and recent ideas are summarized in a brief historical recast in the Supplementary materials.
