Fourier Transform Spectroscopy of the O2 Herzberg Bands. III. Absorption Cross Sections of the Collision-Induced Bands and of the Herzberg Continuum

Abstract

Absorption spectra of molecular oxygen were measured in the laboratory under temperature and pressure conditions prevailing in the Earth's atmosphere. Spectra of pure O 2 , O 2 ϩ N 2 , and O 2 ϩ Ar were recorded in the 41 700 to 33 000 cm Ϫ1 region (240 -300 nm) at a maximal optical path difference of 0.45 cm using a Fourier transform spectrometer and a multiple reflection gas cell. The different components of the spectra, namely the discrete bands of the three Herzberg systems, the Herzberg continuum, and the collision-induced diffuse Wulf bands, were separated. The contribution of the Herzberg bands was first subtracted using the line parameters determined previously [A. Jenouvrier, M.-F. Mérienne, B. Coquart, M. Carleer, S. Fally, A. C. Vandaele, C. Hermans, and R. Colin, J. Mol. Spectrosc. 198, 136 -162 (1999)] from high-resolution data. Spectra recorded at various pressures then made it possible to determine by linear regression the intensity of the Wulf bands and the Herzberg continuum. The characteristics of the Wulf bands have been investigated in details: vibrational analysis, pressure effect, foreign gas effect, and a simulated spectrum are reported. The Herzberg continuum cross section is determined below the dissociation limit. A comparison with literature data is given. The new O 2 absorption cross sections and O 2 -O 2 collision-induced absorption cross sections are useful in connection with atmospheric measurements of ozone and other trace gases in the UV spectral region.

Proposed standardized definitions for vertical resolution and uncertainty in the NDACC lidar ozone and temperature algorithms – Part 2: Ozone DIAL uncertainty budget

“…The absorption by O 2 should be considered only if any of the detection wavelengths is shorter than 294 nm as the interfering absorption relates to the Herzberg continuum, Herzberg and Wulf bands (Jenouvrier et al, 1999;Fally et al, 2000;Merienne et al, 2001). As already mentioned, the O 2 number density N O 2 is assumed to be directly proportional to air number density N a (constant mixing ratio), and therefore should not be considered as an input quantity.…”

“…An approach similar to that used for the other cross section differentials can be used for the O 2 absorption in the region of the Herzberg and Wulf bands (Fally et al, 2000). This interfering absorption only impacts DIAL measurements using wavelengths shorter than 294 nm.…”

A mobile differential absorption lidar to measure sub-hourly fluctuation of tropospheric ozone profiles in the Baltimore–Washington, D.C. region

“…Further uncertainties arise from interfering gases that have similar absorption cross sections at the DIAL wavelengths (Keckhut et al, 2004). Based on standard trace gas profiles (Heikes et al, 1987;Lin and McElroy, 2010) an uncertainty of 1.5 % in overall retrieved ozone has been calculated due to absorption at the DIAL wavelengths by the oxygen dimer (O 2 -O 2 ) interaction (Fally et al, 2000) and smaller than −0.5 % uncertainty due to nitrogen dioxide (NO 2 ) (Bogumil et al, 2003), as well as a smaller than −1.0 % uncertainty due to sulfur dioxide (SO 2 ) (Stark et al, 1999) unless there is a large pollution event or influence from volcanic emission present (Ancellet et al, 1987;McGee et al, 1993). The largest uncertainties from these gases typically arise within the PBL, and this is the uncertainty reported.…”

Oxidative capacity of the Mexico City atmosphere – Part 1: A radical source perspective

“…Absorptions of atmospheric oxygen were eliminated using the interpolation approach of Volkamer et al (1998). In brief, saturation of molecular absorption lines of oxygen in the Herzberg I-III bands were modeled in high-resolution using line parameters from Fally et al (2000), Jenouvrier et al (1999) and Merienne et al (2000Merienne et al ( , 2001, and oxygen column densities of 3.7×10 17 molecules cm −2 and 4.1×10 17 molecules cm −2 to bracket the effect of density variations on oxygen column densities. The collision induced absorption of oxygen in the Wulf bands was fitted using the literature spectra from Bernath et al (1998).…”