Hybrid fs/ps vibrational coherent anti-Stokes Raman scattering for simultaneous gas-phase N2/O2/CO2 measurements

Abstract

Single-shot, 1-kHz measurements of temperatures and mole fraction ratios along with theoretical modeling for gas-phase N2, O2, and CO2 are demonstrated using hybrid femtosecond/picosecond (fs/ps) vibrational coherent anti-Stokes Raman scattering (CARS). The combination of broadband pump and Stokes pulses covers a spectral range over 1800cm-1 while the narrowband probe pulses generated from a quasi-common-path second harmonic bandwidth compressor (QCP-SHBC) resolves the molecular structures with a bandwidth of ∼7cm-1. Temperature results of 1700-2000 K in methane/air fuel-lean flames show state-of-the-art inaccuracies of less than ∼3% and precision less than 2%. Mole fraction ratios inaccuracy at room temperature is ∼5%, and precision at flame temperatures are 6%-8%.