Principle of Mössbauer spectrometry
Mössbauer spectrometry

The phenomenon of nuclear gamma resonance occurs when a gamma photon emitted by an emitting nucleus S when that nucleus de-excites is absorbed by an identical absorbing nucleus A, which then goes into an excited state (figure 1 ). The spectral distribution of emitted and absorbed photons N (E _γ ) is a Lorentzian of energy width Γ called the natural width of the excited nuclear level : $N\left(E_{\text{γ}}\right)=\frac{1}{4}\left[\frac{{\Gamma }^2}{{\left(E_{\text{γ}}-E_{\text{0}}\right)}^2+\frac{{\Gamma }^2}{4}}\right]$