Absolute absorption coefficients of ClONO₂ infrared bands at stratospheric temperatures

Abstract

Fourier-transform absorption spectroscopy has been used in the laboratory to obtain absolute absorption coefficients a(v) in infrared bands of C1ONO2 in the 700-1800 cm -• spectral region. These data have been obtained over a temperature range (213-296 K) corresponding to stratospheric temperatures. The results are therefore applicable to retrievals of stratospheric C1ONO2 from remote-sensing observations. Room temperature absorption coefficients are some 25% larger than previously reported values, and large temperature dependences in the absorption coefficients have been observed. The/21 and/22 bands behave as simple fundamentals of a system which has low-energy vibrational or torsional modes, with little contribution from hot bands over the temperature range used. The intensity in the /22 Q branch increased by 53% over the temperature range 296-213 K. A similar increase was observed for the/24 Q branch, and significant hot-band features were seen in the /23, /24 spectral region. The /24 Q branch and the/22 Q branch were observed to obey the Beer-Lambert law over the range of pressure, temperature, absorber amount, and resolution employed. The absorption coefficients in the/24 Q branch and in the /22 band were modeled by equispaced absorption lines, each characterized by a central frequency, strength, lower-state energy, and pressure-broadened width.

Long‐term trends of inorganic chlorine from ground‐based infrared solar spectra: Past increases and evidence for stabilization

“…[16] Analyses of atmospheric solar spectra with Birk and Wagner [2000] parameters yield improved fits to the ClONO 2 n 4 band Q branch compared to retrievals with previous sets of ClONO 2 spectroscopic parameters [Ballard et al, 1988;Bell et al, 1992]. The better fits to atmospheric measurements are primarily a consequence of the full range of atmospheric temperatures and pressures included in Birk and Wagner's [2000] laboratory measurements (Ballard et al's [1988] measurements were limited to low pressures).…”

Heterogeneous reaction of ClONO<sub>2</sub> with TiO<sub>2</sub> and SiO<sub>2</sub> aerosol particles: implications for stratospheric particle injection for climate engineering

“…The amount of N 2 O 5 in ClONO 2 was minimised because Cl 2 O was in excess. In addition, the vapour pressure (a few millitorr) of N 2 O 5 (Stull, 1947) is > 100 times lower than that of ClONO 2 (∼ 1 torr) at around −76 • C (Schack and Lindahl, 1967;Ballard et al, 1988;Anderson and Fahey, 1990); therefore, even if N 2 O 5 were present in the gas phase, its amount would be negligible compared to ClONO 2 .…”

Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) data processing and atmospheric temperature and trace gas retrieval

“…Systematic errors of C1ONO2 mixing ratios, which are presented in Table 2a, are also relatively high. This is partly due to large uncertainties (20%) of the absorption cross sections that were used to generate the atmospheric emissivity tables [see Ballard et al, 1988]. In addition, there are strong interferences of C1ONO2 with other trace gases and aerosols (see Figure 11a), especially in the lower stratosphere.…”