Overton-region IR registration of ( Si-O)(2)Si=O and ( Si-O)(2)Si < O-2 > C=O groups on the silica surface

IR spectroscopy in a range of 2050-4000 cm(-1) (the range of overtones and composite frequencies) is used to study the groups (=Si-O)(2)Si=O and (=Si- O)(2)Si(O-2)C=O with different isotopic compositions (O-16, O-18, C-12, and C-13). Analysis of the experimental data and quantum-chemical calculations of vibrational spectra for the model compounds are used to identify the IR bands. New data are obtained on the vibrational spectra of these groups. T heir identification is shown to be possible in the spectral range that is c onvenient for the study of silica samples.