Detection of acetylene by electronic resonance-enhanced coherent anti-Stokes Raman scattering
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We report the detection of acetylene (C2H2) at low concentrations by electronic resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS). Visible pump and Stokes beams are tuned into resonance with Q-branch transitions in the v2 Raman band of acetylene. An ultraviolet probe beam is tuned into resonance with the Ã - X̃ electronic transition of C2H2, resulting in significant electronic resonance enhancement of the CARS signal. The signal is found to increase significantly with rising pressure for the pressure range 0.1-8 bar at 300 K. Collisional narrowing of the spectra appears to be important at 2 bar and above. A detection limit of approximately 25 ppm at 300 K and 1 bar is achieved for our experimental conditions. The signal magnitudes and the shape of the C2H2 spectrum are essentially constant for UV probe wavelengths from 233.0 to 238.5 nm, thus indicating that significant resonant enhancement is achieved even without tuning the probe beam into resonance with a specific electronic resonance transition. © Springer-Verlag 2007.
author list (cited authors)
Chai, N., Naik, S. V., Kulatilaka, W. D., Laurendeau, N. M., Lucht, R. P., Roy, S., & Gord, J. R.