open access

https://hdl.handle.net/2115/86863

Temperature dependence of a Raman CO2 densimeter from 23 degrees C to 200 degrees C and 7.2 to 248.7 MPa : Evaluation of density underestimation by laser heating

英語

laser heating

2021-10

John Wiley & Sons

Journal of Raman spectroscopy

52(10)

1744-1757

Unintended local temperature enhancement by excitation laser might change Raman spectral features and potentially lead to misinterpretation of the data. To evaluate robustness of Raman CO2 densimeters in the presence of laser heating, we investigate the relation between temperature (T, degrees C), density (rho, g/cm(3)), and Fermi diad split (Delta, cm(-1)) using a high-pressure optical cell at 23 degrees C to 200 degrees C and 7.2-248.7 MPa. Results indicate that Delta decreases concomitantly with increasing temperature for a constant density in all density regions investigated. This result suggests that the density estimated based on Delta might be underestimated if the fluid is heated locally by the laser. Combining results of earlier studies with those of the present study indicates that the temperature dependence of Delta (|( partial differential Delta/ partial differential T)(rho)|) has a maximum value around 0.6-0.7 g/cm(3). Consequently, at very high densities such as 1.1-1.2 g/cm(3), |( partial differential Delta/ partial differential T)(rho)| is small. Thus, Delta at such densities is less affected by laser heating. However, at densities below approximately 0.7 g/cm(3), although |( partial differential Delta/ partial differential T)(rho)| becomes smaller at lower densities, the relative density decrease becomes larger even for a small density decrease because the density itself becomes smaller. Therefore, at such densities, a density decrease of more than 10% was observed for some fluid inclusions, even at typical laser powers for inclusion analysis. Finally, to accurately estimate the density even in the presence of laser heating, we show that it is effective to estimate the intercept Delta from the correlation between Delta and laser power and substitute it into Delta-rho relations.

学術雑誌論文

Accepted Manuscript

This is the peer reviewed version of the following article : Journal of Raman spectroscopy Volume52, Issue10 October 2021 Pages 1744-1757, which has been published in final form at https://doi.org/10.1002/jrs.6188. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

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