Vibrational Anisotropy and Gol'Danskii–Karyagin Effect in Trimethyltin Cyanide

Abstract

Mössbauer effect measurements have been carried out on (CH₃)₃SnCN in the temperature range $\text{9°}\mathrm{K}\text{\hspace{0.17em}<\hspace{0.17em}T\hspace{0.17em}<\hspace{0.17em}204°}\mathrm{K}$ . From the asymmetry of the intensity of the two components of the quadrupole split spectrum it is possible to calculate the anisotropy in the mean‐square amplitude of vibration of the metal atom parallel and perpendicular to the molecular symmetry axis. Extrapolation of the low‐temperature data to 300°K gives a value of this anisotropy which is in good agreement with the value derived from x‐ray diffraction data. The latter can be used to normalize the temperature‐dependent recoil‐free fraction data which in turn permit an estimate to be made of the anharmonicity of the heavy atom vibration in the low‐and high‐temperature limits. The present data on (CH₃)₃SnCN are in agreement with an oblate electrostatic field ${\mathrm{(V}}_{\mathrm{zz}}\text{>0)}$ around the metal atom and show that the vibrational amplitudes involving this atom approach an isotropic behavior in the low‐temperature limit.