FINE-STRUCTURE OF THE ASYMMETRIC STRETCHING VIBRATION OF DISPERSED OXYGEN IN MONOISOTOPIC GERMANIUM

Dispersed oxygen in Ge leads to the formation of Ge2O ''quasimolecules '' whose,asymmetric stretching mode (nu3), exhibits a remarkable, temp erature-dependent fine structure when examined under the ultrahigh res olution of a Fourier-transform spectrometer. The large number of sharp lines observed arises from the coupling Of nu3 With the low-energy sy mmetric bending nu2 mode; the thermal population of the nu2 levels, to gether with the shifts associated with the isotopes of Ge in their nat ural abundances, underlie its fine structure and temperature dependenc e. By incorporating oxygen in monoisotopic Ge-70, Ge-73, Ge-74, or Ge- 76, the excitation spectrum of the nu2 + nu3 COUPling is selectively s implified. From the temperature dependence of the intensities of the l ines in the fine structure, the energies of the nu2 levels are deduced . The O-18 counterpart of the nu2 + nu3 coupling excitation has been o bserved and a consistent interpretation of the nu2 levels as well as t he shifts of the nu2 + nu3 coupling excitations associated with any is otopic combination of oxygen and Ge is obtained by using an interactio n mass m' = 23.1 amu and a Ge-0-Ge bond angle 2alpha = 111-degrees.