Studies of the O2 3Πg(V) valence states and 3Πg(R) Rydberg state in the Schumann–Runge continuum from ejected and scattered electron spectra

Abstract

Electron‐impact energy‐loss spectra are obtained in O₂ in the energy‐loss range of 7 to 10 eV. These spectra contain some discrete features resulting from scattered electrons following excitation of Rydberg states, and other features from ejected electrons following decay of O₂⁻Feshbach resonances into valence electronic states in the continuum via the reaction e+O₂ (X ³S_g⁻)→(O₂⁻)→O₂ ³R_g(V) +e_ejected. From the known O₂⁻ energies and from measurements of the ejected electron energies, we find the ³R_g(V) state to extend over an energy range of only about 0.20 eV in the Franck–Condon region of the ground state, contrary to some previous experimental and theoretical results. From measurements of scattered electrons, effective excitation functions of several vibrational levels of the ³R_g(R) Rydberg state are obtained. Of the many O₂⁻ Feshbach resonances known to exist in this energy regions, only one decays strongly into the ³R_g(R) state.