New Absorption Spectra of Atomic and Molecular Oxygen in the Vacuum Ultraviolet. II. Rydberg Series from O I(1D2) and O I(1S) Metastable States

We have extended our previous work [J. Chem. Phys. 46, 2213 (1967)] on absorption series from the O I ³P_2,1,0 ground state by measuring and classifying eight series having metastable O I ¹D₂ or ¹S₀ as the lower state. For O I ¹D₂ as the lower state, series have been classified with the following upper states: $$\begin{array}{cc}{(}^2{D}^0{\mathrm{)ns}}^{\prime }:& {}^1{D}_2^0\mathrm{,\hspace{0.17em}}\mathrm{and}{\hspace{0.17em}}^3{D}_2^0,\\ {(}^2{D}^0{\mathrm{)nd}}^{\prime }:& {}^1{F}_3^0{,}^1{D}_2^0\mathrm{,\hspace{0.17em}}\mathrm{and}{\hspace{0.17em}}^1{P}_1^0,\\ {(}^2{P}^0{\mathrm{)ns}}^{\mathrm{\prime \prime }}:& {}^1{P}_1^0,\\ {(}^2{P}^0{\mathrm{)nd}}^{\mathrm{\prime \prime }}:& {}^1{D}_2^0.\end{array}$$ The one series with O I ¹S₀ as the lower state has the upper state (²P⁰)nd″ ¹P⁰₁. The classifications are tentative in some cases. The spectra were observed primarily in absorption through a microwave dischage of a dilute O₂ mixture with helium in a flow system using the Hopfield helium continuum (600–1000 Å) as background. New atomic energy levels for a number of O I singlet terms are given. The metastable ¹D₂ and ¹S₀ atoms disappear rapidly in the downstream region, and it is suggested that they react to form the metastable O₂ molecules (a ¹Δ_g and/or b ¹Σ_g⁺) known to be present in the discharge products.