Knowledge Bank

There has been considerable work done on the photo-absorption spectrum of $O2$ in the 6 to 12 eV region but only very few of the Rydberg states in that region have been identified. The energy-loss region from 6 to 10.5 eV has been studied as a function of incident energy and of scattering angle. The angle and energy dependence observed for the various features in the energy-loss spectra were correlated with the known behavior for transitions of certain symmetry and with the results of improved-virtual-orbital calculations. This analysis has resulted in the identification of the low-lying $(1\Pi g\to 3SCg)3\Pi g$ Rydberg state. The lowest four vibrational levels were observed superposed on the top of the maximum intensity portion of the Schumann-Runge continuum and the state was located at $T_{00} = 8.13 {\pm} 0.02 $eV. The analysis has also resulted in the following tentative identifications for Rydberg states excited from the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi g$ MO: $^{1}{\Sigma}^{-}_{u} at ~ 9.76 \ $eV, $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma u+$ at 9.94 eV, and the ``longest band’’ at 9.97 eV as a $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Sigma u-$.