Anisotropic inelastic nuclear absorption

The dynamics of iron atoms in the ${}^{57}{\mathrm{FeBO}}_3$ single crystal was studied using inelastic nuclear absorption. The energy spectra of nuclear recoil along several crystallographic directions were measured. The densities of phonon states, weighted by the projection of the phonon polarization vector in various directions were derived and the Lamb-Mössbauer factors along these directions were calculated. The projected density of states reveals a pronounced anisotropy, while the Lamb-Mössbauer factor shows no directional dependence.