Dissociation rate constants for absorption by atmospheric oxygen in the Schumann-Runge bands are usually calculated by making line by line calculations of the absorption cross section. The accuracy of the cross sections used in these calculations needs to be tested against experimental data. A transmittance spectrum computed by using a detailed model cross section is compared with a spectrum recorded in the atmosphere and another recorded in the laboratory. It is concluded that details of the atmospheric absorption spectrum can be reproduced with excellent accuracy by the computed cross section.