Improvement of Raman Spectroscopic Densimetry for Carbon Dioxide Fluid

Abstract

We improved Raman spectroscopic densimetry for a CO2 fluid using a micro-Raman spectrometer with high spectral resolution. For precise determination of CO2 density, we obtained Δ, the separation of wavenumbers between two main peaks of the CO2 Raman spectrum, with a precision of ±0.006 cm−1 (1σ). This precision will be enhanced to ±0.003 cm−1 by increasing counts, corresponding to a density precision of ±0.0009 g cm−3, which is approximately one order of magnitude less than that reported in earlier studies.

Pressure measurement and detection of small H2O amounts in high‐pressure H2O–CO2 fluid up to 141 MPa using Fermi diad splits and bandwidths of CO2

“…Consequently, many experimentally obtained results are shown within the measurement error (1σ), but some data were distributed within 1σ to 3σ. Generally, because the measurement error of Δ increases as the count decreases, one reason for scattering data especially on the low‐pressure side might be the low signal/noise ratio of the spectrum obtained from the low‐pressure fluid …”