Visible‐ultraviolet absorption cross sections for NO₂ as a function of temperature

Abstract

A redetermination of the temperature dependence of the absorption cross section (a) of NO 2 in the visible-ultraviolet region (264-649 nm) has been made in order to provide a more reliable data base for the calculation of NO,_ photolysis rates in the atmosphere. Experiments over a wide range of temperatures (--40.6 ø to 124øC) and NO 2 concentrations (3.4 x 10•3-7.3 x 10 • molecules ½m -3) were made at relatively low and high spectral resolutions, employing diode array and Fourier transform spectrometers, respectively. There are three aspects of the temperature dependence which were noted: (1) the integral of a plot of a versus 1/4 (264-649 nm) was essentially independent of temperature; (2) increasing temperature produced a shift of the spectrum toward longer wavelengths, resulting in a small negative temperature dependence of • over the 264-to 400-nm range and a small positive dependence over the 450-to 649-nm range; (3) increasing temperature produced broadening of individual spectral features, resulting in a systematic lowering of peaks and filling of valleys. Recommended cross sections, averaged over 5-nm wavelength intervals, are presented for use in tropospheric NO 2 photolysis rate calculations. EXPERIMENTAL METHODS Many of the experiments described here were carried out in a long-path, temperature-regulated, stainless steel cell, which has been described in detail previously [-Shetter et al., 1987]. The cell is constructed of three concentric tubes, the innermost of which (15.8-cm ID) houses multiple-reflection optics. In all of these studies the adjustable optical path was set at 48.6 m. The inner space between the tubes contains temperatureregulating fluid which is circulated from a temperaturecontrolled bath. The outer space between the tubes serves as an evacuable dewar. In all of the low-resolution studies re-7105

Twilight tropospheric and stratospheric photodissociation rates derived from balloon borne radiation measurements

“…The accuracy of the NO 2 cross sections are estimated to be ±5% (Davidson et al, 1988). Calculation of J[NO 2 ] with the NO 2 cross section of Schneider et al (1987) are about 4-5% smaller then if using Davidson et al (1988). The most re- Talukdar et al (1998).…”

“…The ozone cross section and quantum yields used to calculate J[O( 1 D)] were taken from Bass and Paur (1985) and Matsumi et al (2002) respectively, while the NO 2 cross section and quantum yields were taken from Davidson et al (1988) and DeMore et al (1994) respectively. The accuracy of the NO 2 cross sections are estimated to be ±5% (Davidson et al, 1988). Calculation of J[NO 2 ] with the NO 2 cross section of Schneider et al (1987) are about 4-5% smaller then if using Davidson et al (1988).…”

DOAS for flue gas monitoring—I. Temperature effects in the U.V./visible absorption spectra of NO, NO2, SO2 and NH3

“…43 In the low-temperature range, however, several studies have been performed in applications regarding stratospheric measurements. [43][44][45] When performing spectral recordings of NO* in a heated cell there are several temperaturedependent processes which must be taken into consideration since they may induce errors, i.e., photodissociation, homogeneous and heterogeneous decomposition and conversion to N,O,. Photodissociation was prevented for the measurements around 430 nm by using an optical filter in front of the light source with a cut-off of 410 nm.…”

Cavity Ring-Down and Cavity-Enhanced Detection Techniques for the Measurement of Aerosol Extinction

“…Additional atmospheric extinction in this wavelength region can be caused by nitrogen dioxide (0.26 Mm −1 /ppb NO 2 at 550 nm; e.g., Davidson et al 1988), to a lesser degree by ozone (0.009 Mm −1 /ppb O 3 at 550 nm; e.g., Brion et al 1998), and by aerosol, which tends to be spatially and temporally inhomogeneous. The instrumental challenge is to measure aerosol light extinction with an accuracy better than about 10% of the Rayleigh background level.…”