Introduction

Scientific background

The photolysis rates of different gaseous trace species in the atmosphere are important parameters of profound interest to all atmospheric scientists. This is especially true for chemical models of the atmosphere, as most chemical reactions are directly or indirectly driven by the sun’s radiation. Photolysis rates not only depend upon the intensity of the actinic flux, but also upon the photochemical and photophysical properties of the absorbing molecules. Photodissociation frequencies are governed by the wavelength dependent quantum yield of the photolysis processes and the absorption cross sections of the absorbing species. Both parameters are wavelength dependent, whereby the absorption cross sections may display temperature dependence and the product quantum yields pressure dependence. Thus, for the numerical determination of the photolysis rate of a specific species, the exact knowledge of the absorption spectrum and the product quantum yield under atmospheric conditions is essential. In addition, the experimental determination of kinetic and photochemical parameters of many elementary reactions requires the precise knowledge of the absorption cross sections of many species.

Database at MPI-Mainz

The MPI-Mainz-UV-VIS Spectral Atlas is a comprehensive collection of absorption cross sections for gaseous molecules and radicals, primarily relevant to atmospheric research, from measurements performed during the last nine decades.

The database currently contains more than 4800 data files for more than 800 species and more than 2000 graphical representations.

General features

• Molecules organized by categories
• Numerical data in tables per species and author
• Plots of comparison of spectra per species obtained by several authors
• Bibliography
• Comments on supplementary information
• Search programs for
  - Chemical Formula
  - Species Name
  - Authors
• Additions, modifications and changes in text and plots not possible by outside users
• Copyright protected

The individual data sets were collected from the original publications, either copied from tabulations, or read from figures in those cases where numerical data could no longer be obtained. Other sources rely on the internal databases of several research centers dealing with atmospheric chemistry and/or molecular spectroscopy. Numerous excellent high-resolution spectra were obtained from personal communications with the scientists.

Goal and general use

The MPI-Mainz-UV-VIS Spectral Atlas is made available to the scientific community by interactive access through the web.
The MPI-Mainz-UV-VIS Spectral Atlas allows free access to the database, visualization, extraction, and ability to download spectral data.
The MPI-Mainz-UV-VIS Spectral Atlas is protected for external modification. Any information taken from the Spectral Atlas and used for further publication should be referenced as

Hannelore Keller-Rudek, Geert K. Moortgat,
MPI-Mainz-UV-VIS Spectral Atlas of Gaseous Molecules,
www.atmosphere.mpg.de/spectral-atlas-mainz

Status: Oktober 2009