CO2 laser photoacoustic measurements of ethanol absorption coefficients within infrared region of 9.2–10.8 μm

• New set of absorption coefficients for ethanol vapors in nitrogen atmosphere
• Measurements are performed by laser photoacoustic spectroscopy.
• The absorption spectrum overlaps with 54 lines of CO2 laser in 9.2–10.8 μm range.
• All the experimental conditions were extremely well controlled.

Absorption coefficients of the ethanol vapors at atmospheric pressure and room temperature were measured by photoacoustic technique using a cw, line-tunable, frequency-stabilized CO2 laser as radiation source. The spectrum of the employed CO2 laser includes 54 lines with wavelengths in the infrared region of 9.2–10.8 μm and power levels up to 4.7 W. Measurements revealed a predominant absorption for ethanol within 9.4 μm band of the CO2 laser spectrum, where the highest values of the absorption coefficients were recorded: 3.68 cm− 1 atm− 1 at 9R(20) line and 3.65 cm− 1 atm− 1 at 9R(22) line. The estimated detection range covers six orders of magnitude, from a minimum of 30 ppbV to a maximum of 4% concentration of ethanol in nitrogen, which proves the suitability of the photoacoustic technique for accurate measurements of the ethanol concentration in various applications.

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