Detection of C<sub>2</sub>H<sub>2</sub> via UV photo-fragmentation, followed by monitoring the C<sub>2</sub> <i>d</i><sup>3</sup>Π<sub>g</sub>-<i>a</i><sup>3</sup>Π<sub>u</sub> fluorescence, is explored at atmospheric pressure and at temperatures of 295 K, 600 K, and 800 K, for excitation wavelengths 210 to 240 nm using a broadband laser source (∼3 cm<sup>-1</sup> fwhm). At the lower temperature, C<sub>2</sub> emissions correlate closely with C<sub>2</sub>H<sub>2</sub> Ã ← X absorption bands, and the excitation spectra suggest a higher-transition probability for the v<sup>"</sup><sub>4</sub> = 2 and 3 states than for the v<sup>"</sup><sub>4</sub> = 0 and 1 states. As temperature increases, the excitation spectra exhibit a higher nonresonant background.
Paul C. Miles, Bo Li, Zhongshan Li, and Marcus Aldén, "Atmospheric Pressure Acetylene Detection by UV Photo-Fragmentation and Induced C2 Emission," Appl. Spectrosc. 67, 66-72 (2013)