Knowledge Bank

The 2800-2400 {\AA} absorption of $O2$ in solid solutions is dominated by the $C3\Delta u\leftrightarrow 3\Sigma g-$ transition, unlike $O2$ in the gas phase, Isotopically resolved excitation spectra of v^{\prime}=O $C3\Delta 1$ emission in solid $N2$ host provide detailed vibrational and electronic $C3\Delta$ spectroscopic parameters. The data establish absolute vibrational numbering for $c3\Delta$ and $c1\Sigma$, in the gas phase as well as in the solid. A progression of perturbations between v^{\prime} $C3△2$ and $v\prime -2A3\Sigma u+$ is analyzed to show that this host-Induced, symmetry-forbidden interaction is characterized by a matrix element H = 27 $cm-1$. Vibrational relaxation within both singlet and triplet excited states is ``fast” in $N2$, Ar, and Xe hosts. It is experimentally proven that these spectra occur in isolated $O2$ monomers. Excited $O2$ photo-chemistry appears to occur in Xe host, but not in $N2$ host.