Temperature Dependence of the NQR Frequencies in SnBr_4 and SnI_4

The nuclear quadrupole resonances for ^<81>Br and ^<127>I were observed in polycrystalline SnBr4 and SnI_4 at temperature between liquid nitrogen and room temperature. In SnBr_4 the phase transition between α-form and β-form was observed at 13.5±0.5℃. In α-SnBr_4 the assignment was discussed in a qualitative way in terms of the anisotropy in the thermal motions of molecule. In β-SnBr_4 and SnI_4 the splitting of the resonance signals was correlated with molecular oscillations and intermolecular interactions.