Integrated band intensities and absorption cross sections of phosgene (Cl2CO) in the mid-infrared at 199, 250 and 300 K

Abstract

Integrated band intensities and absorption cross-sections of phosgene (Cl2CO) have been measured at different temperatures (199, 250 and 300 K) to support remote sensing applications, particularly for an accurate quantification of Cl2CO in the Earth's atmosphere. To our knowledge and prior to this study, no previous work has examined the temperature dependence of the phosgene integrated band intensities. Series of N2-broadened spectra of phosgene were recorded from 525 to 2400 cm−1, at a resolution of 0.1 cm−1, using a Bruker IFS125HR Fourier transform spectrometer located at the LISA facility in Créteil, France. The pressure of each phosgene vapor sample was measured using high precision capacitance manometers and a minimum of six sample pressures were recorded for each temperature. The samples were introduced into an especially designed, short optical path length (5.10 ± 0.01 cm), coolable cell, that was mounted inside the spectrometer. From these spectra, integrated band intensities for six spectral regions corresponding to the ν2/ν4, ν5, ν2 + ν6, ν2 + ν5, 2ν5 and ν1 bands were obtained from room temperature down to 199 K. We discussed and quantified error sources and, on average, the estimate accuracy for the measured integrated band intensities is equal to 4%. Measurements at room temperature were compared with previously reported values. Our results at 300 K, show an excellent agreement (better than 4%) with the Hopper et al. J Chem Phys (1968) values, agree reasonably well with those from the PNNL database (better than 9% for the stronger ν1 and ν5 bands of atmospheric interest), but depart strongly from the measurements of Lovell and Jones J Mol Spectrosc (1960) for which there are differences between 20 and 43%. In addition, our results at low temperatures show a non-negligible temperature dependence (7.5 to ∼31%, depending on the bands, between 300 and 199 K), probably due to the presence of hot bands and possible overlapping neighboring bands such as overtones and combination/difference bands. To better understand these temperature variations a detailed high resolution investigation of pure Cl2CO spectra over a wide range of temperature would be necessary.