Quantitative measurements of broad-band mid-infrared absorption spectra of formaldehyde, acetaldehyde, and acetone at combustion-relevant temperatures near 5.7 µm

Abstract

Temperature-dependent absorption cross sections of formaldehyde, acetaldehyde, and acetone are presented for their CO stretching bands near 5.7 µm. The measurement methodology employs a broad-scan, rapid-tuning EC-QCL in conjunction with shock tube facilities and can provide quantitative spectroscopic information with an average spectral resolution of 0.6 cm−1 at a tuning rate in excess of 30 cm−1/ms. The absorption spectrum of formaldehyde in the ν2 vibrational band is reported at 998 K and 3.8 atm, showing reasonable agreement with spectral simulations based on HITRAN 2016. The residuals are ascribed to the emergence of hotbands and high-J rovibrational transitions at elevated temperatures. The first high-temperature absorption cross section measurements of acetaldehyde and acetone are reported near atmospheric pressure at combustion-related temperatures up to 1000 K, with strong temperature broadening observed in the measured spectra. The results presented are archived in the Stanford ShockGas-IR database and are expected to be useful in future spectroscopic studies.