Shift of CO2-I absorption bands in diamond: A pressure or compositional effect? A FTIR mapping study

Infra-red maps and profiles with high spatial resolution were obtained for two single crystal diamonds pronounced CO2 IR absorption peaks. Detailed examination allows unambiguous assignment of the spectral features to solid CO2-I phase. It is shown that distribution band positions, intensities widths in sample follows regular patterns not chaotic as was suggested previous works where spectra a few individual spots analysed. Consequently, pressure effects alone fail explain all observed shifts bands. Experimental data can be explained by presence impurities (such water, N2, etc.) trapped CO2. This implies spectroscopic barometry microinclusions diamond may subject poorly controlled bias. However, still possible if Davydov splitting {\nu}2 unequivocally observed, this indicates purity ice.