Picosecond time-resolved pure-rotational coherent anti-Stokes Raman spectroscopy in sooting flames

The development of time-resolved dual-broadband pure-rotational coherent anti-Stokes Raman spectroscopy using picosecond laser pulses is investigated for use in the study of highly sooting flames. Axi-symmetric ethylene and propane diffusion flames were studied. Suppression of nonresonant and Raman resonant interference signals is demonstrated by delaying the probe pulse beyond the temporal envelope of the pump pulses, and these spectra are compared with those obtained using conventional polarization-based interference suppression techniques. Flame profiles for both temperature and the O2O2 to N2N2 ratio are obtained. Evaluated temperatures are corrected for delay-induced spectral heating and compared to published thermocouple measurements.