Effect of molecular motions in liquids on Mössbauer relaxation spectra

The simultaneous effects on Mössbauer spectra of translational motion of the nucleus and the relaxation phenomenon arising out of rotating electric-field-gradient axes, due to molecular motions in liquids, are studied in a stochastic-theory model. The rotational motion is assumed to be described by a diffusion equation. For ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, a simple closed-form expression for the line shape is obtained which is valid for the entire range of motion.