Decay mechanism of the nu(3) 865 cm(-1) vibration of oxygen in crystalline germanium

The nu(3) (862.5 cm(-1)) vibration of oxygen in crystalline germanium is shown to decay into one nu(1) local mode of the oxygen center plus two lattice modes. This description predicts increases in the linewidths in O-16-doped germanium, and decreases in the linewidths in O-18-doped germanium, as the Ge mass in the Ge-O-Ge complex increases, in agreement with observation. The decay time is expected to vary only slightly with the isotope of oxygen, as observed, and the smallest reported linewidths are consistent with the measured decay times.