Measurements of benzene concentration by difference-frequency laser absorption spectroscopy

Measurements of benzene concentration based on high-resolution laser absorp tion spectroscopy by use of the R(6) transition in the nu (4) fundamental v ibrational band near 14.8 mum (676.6 cm(-1)) are reported. These measuremen ts were performed with a tunable continuous-wave, mid-infrared spectroscopi c Light source that employs difference-frequency mixing of two Ti:sapphire lasers in a GaSe nonlinear optical crystal. A minimum benzene concentration detection of similar to 11.5 parts in 10(9) was realized at a reduced pres sure of 40 mbars. (C) 2000 Optical Society of America OCIS codes: 010.1120, 120.6200, 190.2620, 300.6340, 300.6360.