An Analytical Expression for Fractional Absorption in MÖssbauer Spectroscopy

Removing the restriction that the line widths ( Gamma_s and Gamma_a) of a source and an absorber be equal, we have obtained an exact analytical expression for the fractional intensity of absorbed gamma -rays in MOumlssbauer spectroscopy. This expression is compact and consists of three terms; the first two are known in the literature for the case Gamma_s=Gamma_a, and the third term contains a simple sum of higher-order terms arising from Gamma_s ne Gamma_a. We provide quantitative analyses and a discussion of the contribution from this third term and its effect on the fractional absorption of a MOumlssbauer spectral line.