Impurity-host to host-host coupling force constant ratio for 57Fe in rare gas solids

Lattice dynamical studies of the Moessbauer recoilless fraction and SOD for 57Fe embedded in Ar, Kr, and Xe, are reported by McNab and coworkers, using the rare gas matrix isolation technique. According to them, the f-values for the various hosts are nearly the same. Making use of the experimentally determined phonon frequency distribution functions for these hosts, an attempt is made to calculate the f-values in the framework of the Mannheim model. The anharmonicity correction is also applied for temperatures beyond 5 K. It is found that the values of the ratio of the impurity-host to the host-host coupling-force constants in these lattices change in a way that the f-values and SOD remain the same, thereby indicating their independence of the host. In accordance with the expectation, no localized modes are found due to the weak binding of the impurity to the host. (author)