A RAMAN-SPECTROSCOPIC STUDY OF H/D ISOTOPICALLY SUBSTITUTED HYDROUS ALUMINOSILICATE GLASSES

We have obtained high quality Raman spectra for two H/D isotopically substituted hydrous aluminosilicate glasses with compositions along the NaAlSi3O8 -SiO2 join. Consistent with the results of previous studies, the isotope shift for the band near 900 cm-1, whose intensity grows with increasing water content, is extremely small: nu(H)/nu(D)=1.004+/-0.004. The lack of a definite H/D isotope shift for this band does not, however, preclude its association with a vibration of a hydrous species in the glass, because of likely strong coupling between different vibrational modes of hydrated framework species. The 900 cm-1 band could well be due to a T - OH (T = Si, Al) stretching or bending vibration in the hydrous glass, as required by the presence of a combination band near 4500 cm-1 in near-infrared spectra.