S-branch CARS applicability to thermometry

Area of Science:

• * Molecular Spectroscopy
• * Laser-based diagnostics
• * Physical Chemistry

Background:

• * Coherent Anti-Stokes Raman Scattering (CARS) is a powerful technique for thermometry.
• * S-branch CARS spectra of Nitrogen (N2) offer potential for accurate temperature measurements.
• * Understanding pressure and temperature effects is crucial for practical applications.

Purpose of the Study:

• * To investigate the pressure and temperature dependence of N2 S-branch CARS spectra.
• * To evaluate the feasibility and accuracy of S-branch CARS thermometry.
• * To explore practical methods for S-branch CARS thermometry.

Main Methods:

• * Experimental measurement of background-free S-branch CARS spectra of N2.
• * Analysis of spectral data across a temperature range of 300-700 K and pressure range of 1-20 atm.
• * Investigation of collisional narrowing effects on spectral lines.

Main Results:

• * Collisional narrowing in S-branch CARS spectra was found to be negligible.
• * Individual S-branch lines were clearly resolved across the entire experimental range.
• * Temperature determination using peak ratios was demonstrated to be unequivocal.

Conclusions:

• * S-branch CARS thermometry of N2 is a viable technique for accurate temperature measurements.
• * The negligible collisional narrowing simplifies spectral analysis.
• * Dual narrowband Stokes CARS is a practical approach for implementing S-branch CARS thermometry.