>> Sturcture Dependent Lifetimes

The lifetimes of the asymmetric stretch mode of interstitial 16O and 17O isotopes in Si are measured at 10 K directly by time-resolved, transient bleaching spectroscopy to be 11.5 and 4.5 ps, respectively.

A calculation of the three-phonon density of states shows that the 17O mode lies in the highest phonon density resulting in the shortest lifetime. The interaction between the local modes and the lattice vibrations is discussed according to the activity of phonon combinations.

The lifetime of the asymmetric stretch mode is measured to be T1 = 125 ± 10 ps at 10 K, i.e., ~10 times longer than in Si.. Since the absorption lines of the 16Oi mode for different Ge isotopes are very close, our laser pulses can measure only an average lifetime. This corresponds to an average linewidth of 0.04 cm^-1 in good agreement with infrared absorption measurements.