Knowledge Bank

Predissociation in the Schumann-Range bands of molecular oxygen plays an important role in the production of atmospheric $ozoneh$. However, the region of the Schumann-range bands near the dissociation limit $(\nu \prime =18-22)$ has only been partially analysed in the past. This has been due to the difficulties associated with obtaining accurate intensity and width measurements with spectrographic techniques, and the presence of main” and extra” lines associated with rotational perturbations. Our use of the non-linear optical technique of four-wave difference-frequency mixing (FWDFM) has enabled this region of the Schumann-Range bands (from 175-178nm) to be studied in unprecedented detail, with sub-Doppler resolution inabsorption. Recent measurements using FWDFM have enabled analysis of the $\nu \prime =16-18$ bands, with interpretation of the perturbations present in the region. The current investigation involves the study of those lines from $\nu \prime =19-22$. Preliminary analysis of the $\nu \prime =19$ band rotational lines confirms the presence of perturbations in the $F3$ levels, possible caused by interactions with the $C\prime 3\Pi$ state. Results will be presented here on the recent findings in this region.