Effect of pressure and temperature on Raman shifts of methane in CH_4-H_2O vapor phase

摘要

Raman spectroscopy is an extremely useful tool in fluid inclusion studies; however, it is important to recognize that the characteristics of Raman-active species spectra are associated to their environments, therefore, the pressure and temperature dependence of characteristic Raman spectra of geologic fluids is the key for the correct interpretations of the physico-chemical properties of fluid inclusions. Previous studies of methane-containing gases have shown that methane peak positions shifted to lower wavenumbers with increasing pressure, and such relationship had been used to calculate the pressure of CH_4 vapor in the inclusion near room temperature (Chou et al., 2006). However, little is known about the temperature effect on this Raman shift-pressure relationship. In this study, Raman spectra of methane in the vapor phase for methane-water system were studied at pressures up to 36.82 MPa from room temperature up to 200°C.