Temperature Dependence of Nuclear Quadrupole Resonance in Cuprous Oxide

The pure nuclear quadrupole resonance frequencies of ⁶³Cu and ⁶⁵Cu nuclei in Cu₂O have been measured from 350 down to 4^∘{}K. Below 140^∘{}K the dependence deviates from linearity. A model based on vibrations of the Cu nuclei transverse to the O-Cu-O axis is shown to be consistent with the experiments. The frequency ω of the transverse vibrational band is derived to be 97±{}7 cm^-1.