Detection of Long-Lived Excited States of Molecules by Penning Ionization

Abstract

A method for the detection of excited neutral long‐lived particles by ionization of properly chosen molecules with different ionization potential was developed and applied to the study of long‐lived excited states of H₂, N₂, CO, and O₂. Results in H₂ and O₂ confirm previous findings. In N₂ a new state was found which releases in the transition to the ground state an energy of ∼11.4–11.6 eV. Also determined was its separated excitation function. This state is formed partly through a resonance capture of an exciting electron and subsequent decomposition of the unstable negative excited molecular ion N₂^−*. In CO a new long‐lived excited state at ∼10 eV was detected, and the existence of another, higher lying, state was suggested.