Detection of O&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; absorption around 328 and 419 nm in measured atmospheric absorption spectra

Johannes Lampel,Udo Frieß,Denis Pöhler,Ulrich Platt,Stefan Schmitt,Thomas Wagner,Johannes Zielcke

doi:10.5194/acp-18-1671-2018

Abstract

Abstract. Retrieving the column of an absorbing trace gas from spectral data requires that all absorbers in the corresponding wavelength range are sufficiently well known. This is especially important for the retrieval of weak absorbers, whose absorptions are often in the 10−4 range. Previous publications on the absorptions of the oxygen dimer O2–O2 (or short: O4) list absorption peaks at 328 and 419 nm, for which no spectrally resolved literature cross sections are available. As these absorptions potentially influence the spectral retrieval of various trace gases, such as HCHO, BrO, OClO and IO, their shape and magnitude need to be quantified. We assume that the shape of the absorption peaks at 328 and 419 nm can be approximated by their respective neighbouring absorption peaks. Using this approach we obtain estimates for the wavelength of the absorption and its magnitude. Using long-path differential optical absorption spectroscopy (LP-DOAS) observations and multi-axis DOAS (MAX-DOAS) observations, we estimate the peak absorption cross sections of O4 to be (1.96 ± 0.20) × 10−47 cm5 molec−2 and determine the wavelength of its maximum at 328.59 ± 0.15 nm. For the absorption at 419.13 ± 0.42 nm a peak O4 cross-section value is determined to be (5.0 ± 3.5) × 10−48 cm5 molec−2.

Highlights

The collision-induced absorption of the O2–O2 dimer needs to be considered in various wavelength regions for in situ and remote sensing absorption spectroscopy of various atmospheric trace gases
The O4 absorption governs the budget of tropospheric singlet oxygen O2(1 ) (Schurath, 1986), which can potentially impact the oxidation of atmospheric trace gases, like CO (Platt and Perner, 1980) and SO2 (Sorokin, 2010)
4 Results 4.1 Peak positions As we assume the maximum of the O4 absorption peak at 328.2 nm (Salow and Steiner, 1936) and at 419 nm (Ellis and Kneser, 1933), its exact wavelengths needed to be determined again from the measurements

Summary

Introduction

The collision-induced absorption of the O2–O2 dimer (or short: O4) needs to be considered in various wavelength regions for in situ and remote sensing absorption spectroscopy of various atmospheric trace gases. Most of the absorption peaks in the UV–vis range of liquid oxygen can be found for gas-phase oxygen, as measured by Janssen (1885), Salow and Steiner (1936), Greenblatt et al (1990), Hermans et al (1999), Thalman and Volkamer (2013) and others. It was first observed in the atmosphere by Perner and Platt (1980). A clear difference of the relative magnitude for the absorption of O4 in the liquid and gas phases cannot be seen from the available data

Methods

Results

Conclusion