Broadband d₂ coherent anti–stokes raman spectroscopy for single–shot pressure and temperature determination with a fabry–perot etalon

A method is demonstrated that employs a Fabry–Perot etalon to modulate a broadband coherent anti-Stokes Raman spectroscopy signal beam spatially to obtain enhanced resolution and spectral information for single–shot measurements of pressure and temperature. Resulting images are analyzed by; first, fits to Fabry–Perot patterns for single rovibrational lines; second, a line-shape analysis for a single rovibrational line; and third, a mapping of the Fabry–Perot channel spectra to a linear spectrum. Measurements of the D₂ Raman Q–branch lines were made for a D₂ in Ar mixture to take advantage of the large pressure shift and rovibrational line spacing. Peaks are located to better than 0.5% of the free spectral range of the etalon (approximately 0.01 cm^-1) and a quantitative analysis of the pressure shifting and broadening is determined for the 1–10-MPa range. Finally, temperature and pressure determination using a band-fitting analysis is demonstrated.