Measurements of benzene concentration based on high-resolution laser absorption spectroscopy by use of the <i>R</i>(6) transition in the ν<sub>4</sub> fundamental vibrational band near 14.8 μm (676.6 cm<sup>−1</sup>) are reported. These measurements were performed with a tunable continuous-wave, mid-infrared spectroscopic light source that employs difference-frequency mixing of two Ti:sapphire lasers in a GaSe nonlinear optical crystal. A minimum benzene concentration detection of ~11.5 parts in 10<sup>6</sup> was realized at a reduced pressure of 40 mbars.
© 2000 Optical Society of America
(010.1120) Atmospheric and oceanic optics : Air pollution monitoring
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(190.2620) Nonlinear optics : Harmonic generation and mixing
(300.6340) Spectroscopy : Spectroscopy, infrared
(300.6360) Spectroscopy : Spectroscopy, laser
Weidong Chen, Fabrice Cazier, Frank Tittel, and Daniel Boucher, "Measurements of Benzene Concentration by Difference-Frequency Laser Absorption Spectroscopy," Appl. Opt. 39, 6238-6242 (2000)