Ultraviolet Laser Raman Scattering for Temperature Measurement in Atmospheric Air Microdischarges

Vibrational Raman scattering for temperature measurement within a dc microdischarge in atmospheric pressure air has been investigated using a pulsed ultraviolet laser. The Raman signal analysis method involved monitoring Q-branch signals originating from multiple N$_{2}$(X) vibrational states populated in the microdischarge. The translational temperature of N$_{2}$(X) in the microdischarge was calculated using the total Raman signal intensity calibrated with room temperature air. Also, the distribution of Q-branch intensities among vibrational states allowed for direct measurement of the vibrational temperature of N$_{2}$(X). Raman scattering results are compared to passive optical emission spectral analyses of the N$_{2}$ second positive system from which the rotational and vibrational temperatures of the N$_{2}$(C) excited state were also calculated. A comparison of the N$_{2}$(X) and N$_{2}$(C) temperatures derived from Raman scattering and emission spectroscopy, respectively, is presented. This work was supported by the Air Force Office of Scientific Research.