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Depolarization Ratios of Methane Raman Bands as a Function of Pressure
1Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch of the Russian Academy of Sciences, 634055 Tomsk, Russia.
Molecules (Basel, Switzerland)
|April 26, 2020
Summary
We measured methane Raman spectra, finding its depolarization ratio increases with pressure. This precise data aids high-pressure polarizability calculations and natural gas analysis.
Area of Science:
- Molecular spectroscopy
- Quantum chemistry
- Physical chemistry
Background:
- Accurate methane polarizability data is crucial for high-pressure applications.
- Raman spectroscopy is a key technique for analyzing gas composition, including natural gas.
Purpose of the Study:
- To precisely measure the intensities and depolarization ratios of methane Raman bands (ν1, ν2, ν3) under pressure.
- To provide accurate data for high-pressure methane polarizability calculations.
- To improve methane Raman spectral analysis for natural gas composition determination.
Main Methods:
- Measurement of polarized and depolarized methane Raman spectra.
- Analysis of Q-branch intensities for ν1, ν2, and ν3 bands.
- Pressure range: 1-60 atm.
- Precise determination of ν1 band intensities, accounting for overlapping ν3 band contributions.
Main Results:
- The pressure dependence of depolarization ratios for ν2 and ν3 bands was found to be negligible.
- The depolarization ratio of the ν1 band shows a pressure-dependent increase, reaching ~0.0045 at 60 atm.
- The obtained data offers higher precision than previous studies.
Conclusions:
- The study provides valuable, high-precision data on methane Raman spectra at elevated pressures.
- The findings support the calculation of methane polarizabilities under high-pressure conditions.
- The results enhance the capability of Raman spectroscopy for accurate natural gas composition analysis.
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