Photodissociation of O2 and N2 in the Far Vacuum uv and Production of Excited O and N Atoms

Photodissociation of O₂ and N₂ yielding highly excited O and N atoms has been investigated in the region from 1000 to 450 Å by observing the fluorescence of fragments in the region between 1500 and 1100 Å. Fluorescence intensities were measured as a function of the incident wavelength. The following dissociation processes have been identified: $${\mathrm{O}}_2\mathrm{\hspace{0.17em}\to \hspace{0.17em}}\mathrm{O}{\text{(3s}}^3{S}^0\mathrm{)\hspace{0.17em}+\hspace{0.17em}}\mathrm{O}{(}^3\mathrm{P),}$$ $$\mathrm{\to \hspace{0.17em}}\mathrm{O}{\text{(3p}}^3\mathrm{P)\hspace{0.17em}+\hspace{0.17em}}\mathrm{O}{(}^3\mathrm{P),}$$ $$\mathrm{\to \hspace{0.17em}}\mathrm{O}{\text{(3s}}^1{D}^0\mathrm{)\hspace{0.17em}+\hspace{0.17em}}\mathrm{O}{(}^3\mathrm{P),}$$ $${\mathrm{N}}_2{\text{\hspace{0.17em}→\hspace{0.17em}N(3s}}^4\mathrm{P)\hspace{0.17em}+\hspace{0.17em}}\mathrm{N}{(}^4{S}^0\mathrm{),}$$ $${\text{→\hspace{0.17em}N(3s}}^2\mathrm{P)\hspace{0.17em}+\hspace{0.17em}}\mathrm{N}{(}^2{D}^0\mathrm{).}$$ The threshold wavelengths of these processes coincide closely with the corresponding dissociation energies. The fluorescence intensities of the 1305‐ and 1200‐Å resonance lines of O and N, respectively, were calibrated and absolute cross sections for the production of $\mathrm{O}{\text{(3s}}^3{S}^0)$ and $\mathrm{N}{\text{(3s}}^4\mathrm{P)}$ have been determined. Depending on the incident wavelength, cross sections of up to 4 × 10⁻¹⁸ and 5 × 10⁻¹⁹ cm² are found for the $\mathrm{O}{\text{(3s}}^3{S}^0)$ and $\mathrm{N}{\text{(3s}}^4\mathrm{P)}$ production, respectively.