Precision evaluation of Raman densimetry for carbon dioxide: improvement by correction for the drift effect

Abstract

To evaluate the precision of the wavenumber difference between the two main Raman bands of CO2 (designated as Δ, an index of CO2 density), we performed theoretical calculations for the uncertainties of the peak positions of the CO2 Raman bands, and measured Raman spectra of CO2 under the conditions used for the calculations. The Δ precision improves with increased peak intensity, but the peak intensity–precision relation does not hold beyond an intensity threshold corresponding to the measurement time of 1–2 min. Correction for temporal variation of Δ by fitting a linear function to the data distribution improved the Δ precision to ±0.0005cm−1 at best, corresponding to CO2 density precision as ±0.00015g/cm3.