H chirped-probe-pulse femtosecond coherent anti-Stokes Raman scattering thermometry at high temperature and pressure.

This article describes the development and application of hydrogen (H) chirped-probe-pulse femtosecond coherent anti-Stokes Raman scattering (CPP fs CARS) in high-temperature and high-pressure conditions. H fs CARS thermometry was performed in Hencken burner flames up to 2300 K, as well as in a heated gas-cell at temperatures up to 1000 K. It was observed that the H fs CARS spectra are highly sensitive to the pump and Stokes chirp.

Two-color polarization spectroscopy measurements of Zeeman state-to-state collision induced transitions of nitric oxide in binary gas mixtures.

We investigated collision induced transitions in the (0, 0) band of the A2Σ+-X2Π electronic transition of nitric oxide (NO) using two-color polarization spectroscopy (TCPS). Two sets of TCPS spectra for 1% NO, diluted in different buffer gases at 295 K and 1 atm, were obtained with the pump beam tuned to the R11(11.5) and OP12(1.

Broadband ultrafast-laser-absorption spectroscopy for multi-hydrocarbon measurements near 3.3 µm in flames.

This paper presents the development and application of a broadband ultrafast-laser-absorption-spectroscopy (ULAS) technique operating in the mid-infrared for simultaneous measurements of temperature, methane ( ), and propane ( ) mole fractions. Single-shot measurements targeting the C-H stretch fundamental vibration bands of and near 3.3 µm were acquired in both a heated gas cell up to ≈650 and laminar diffusion flames at 5 kHz.

Background suppression for CARS thermometry in highly luminous flames using an electro-optical shutter.

An electro-optical shutter (EOS), comprising a Pockels cell located between crossed-axis polarizers, is integrated into a nanosecond coherent anti-Stokes Raman scattering (CARS) system. The use of the EOS enables thermometry measurements in high-luminosity flames through significant reduction of the background resulting from broadband flame emission. A temporal gating ≤100 ns along with an extinction ratio >10,000:1 are achieved using the EOS.

Simultaneous Temperature and Pressure Measurements in Compressible Flow Using Nanosecond O Coherent Anti-Stokes Raman Spectroscopy.

Simultaneous pure-rotational coherent anti-Stokes Raman spectroscopy (PRCARS) and vibrational O CARS spectroscopy (VCARS) were performed at elevated pressure and lowered temperature conditions in non-reacting compressible flow. We applied dual-pump CARS in a three-laser, three-color configuration to simultaneously acquire the PRCARS and VCARS spectra of O PRCARS spectra provide excellent sensitivity to temperature at relatively low temperatures. Pressure was extracted using the differential response of collisional effects in the PRCARS and the VCARS spectra.