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, temperature-dependent fine structure when examined under the ultrahigh resolution of a Fourier-transform spectrometer. The large number of sharp lines observed arises from the coupling Of nu3 With the low-energy symmetric bending nu2 mode; the thermal population of the nu2 levels, together with the shifts associated with the isotopes of Ge in their natural abundances, underlie its fine structure and temperature dependence. By incorporating oxygen in monoisotopic Ge-70, Ge-73, Ge-74, or Ge-76, the excitation spectrum of the nu2 + nu3 COUPling is selectively simplified. From the temperature dependence of the intensities of the lines in the fine structure, the energies of the nu2 levels are deduced. The O-18 counterpart of the nu2 + nu3 coupling excitation has been observed and a consistent interpretation of the nu2 levels as well as the shifts of the nu2 + nu3 coupling excitations associated with any isotopic combination of oxygen and Ge is obtained by using an interaction mass m' = 23.1 amu and a Ge-0-Ge bond angle 2alpha = 111-degrees.