Temperature Dependent Absorption Cross‐sections and Atmospheric Photolysis Rates of Nitric Acid

Abstract

Absorption cross‐sections for HNO3 have been measured in the wavelength region 220–340 nm, using a dual‐beam diode array spectrometer, with a spectral resolution of 0.3 nm. The results at room temperature were in good agreement with earlier measurements. Absorption over most of the wavelength range showed a distinct temperature dependence, with a decline in cross‐section with decreasing temperature in the range 295–239 K. The results lead to quite large effects on the calculated photodissociation rate of HNO3 in the lower stratosphere, especially at the low temperatures and high solar zenith angles characteristic of the polar winter and spring.

New Estimation of the NOx Snow‐Source on the Antarctic Plateau

“…700 times higher than that in the gas phase ( et al, 2008), 1.50 × 21 10 E (Burkholder et al, 1993) and 1.45 ×   21 2 1 10 cm molecules E at 305 nm (Rattigan et al, 1992). Chu and Anastasio (2003) , support this hypothesis: 1.02 × 8 10 E to 3.12 × 10 10 E molecules…”

“…10 cm molecules E at 305 nm (Rattigan et al, 1992). Chu and Anastasio (2003) measured the absorption cross-section of the nitrate ion around 1.2 ×   20 2 1 10 cm molecules E at Dome C. Therefore, with a cross-section of…”

CH3OCI: UV/visible absorption cross sections, J values and atmospheric significance

“…In addition, the Boltzmann population of the low-lying vibrational states of small molecules which display continuous spectra is unlikely to change significantly over a limited temperature range (compare CH302 [Lightfoot and Jerni-Alade, 1991]) and absorption spectra measured at 200 or 295 K are not expected to be significantly different. Even slight changes in spectral shape may be important for molecules which undergo atmospheric photodissociation following absorption into weak bands far from absorption maxima and which extend into the actinic region, e.g., HNO3[Rattigan et al, 1992; Burkholder et al 1993]. For CH3OC1 this is clearly not the case as photodissociation will occur predominantly at wavelengths close to the long-wavelength maximum at 310 nm, and an absorption spectrum measured at 295 K is sufficient to calculate photolysis rates.The stratospheric photolysis rate constant of CH3OC1 (J), calculated by the method of Lary and Pyle [1991 ] is plotted as a function of zenith angle for pressures of 100 and 30 mbar inFigure 5.…”

Stratospheric ozone depletion during the 1995–1996 Arctic winter: 3-D simulations on the potential role of different PSC types

“…The methodology for derivation of the photolysis constants was described, for instance, by Brasseur et al (1990) or Granier and Brasseur (1992). Several updates have been made to the absorption cross sections of the considered species, including the temperature dependence of the HNO 3 (Rattigan et al, 1992) and the ClONO 2 (Burkholder et al, 1994) cross sections. The photodissociation of bromine compounds was added to the model considering absorption cross sections, as recommended by DeMore et al (1997).…”