Knowledge Bank

Multiconfiguration self-consistent-field wavefunctions are used to calculate the transition moments for the two lowest allowed transitions in $O2$. The transition matrix element for the X-B transition calculated at $Re$ of the ground state corresponds to an oscillator strength of 0.18, in good agreement with the experimental integrated oscillator strength 0.16 of the Schumann-Runge continuum. The transition matrix element to the repulsive valence $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u$ state calculated at $Re$ of the ground state corresponds to an oscillator strength of 0.002. Although the weak $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u$ absorption continuum is masked by the strong Schumann-Runge continuum below 1750 {\AA}, this $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u$ absorption may contribute to the background continuum in the Schumann-Runge band region at low temperature.