Line Strength Measurement Using Optoacoustic Spectroscopy

Summary

Optoacoustic spectroscopy (OAS) is known to be a very sensitive method of determining absorption-coefficients down to 10⁻¹⁰ cm⁻¹.The combination of tunable laser and opto-acoustic detector is well suited for lineshape studies and line strength measurements of different species, as well as for monitoring very small absorber quantities in gaseous mixtures. Using the LS-3 diode laser spectrometer, an acoustically nonresonant OA-cell was sensitive to detect about 44 ppb of carbon monoxide (CO) in nitrogen of 1 bar and room temperature. The strength of the CO-line (1←0, R[7] at 2172.8 cm⁻¹) was found to be 7.16 bar⁻¹cm⁻². The results were used for further “in-situ” investigations on flame diagnostics.