Electroionization spectrum ofO2

Abstract

New structures detected in the electroionization spectrum of ${\mathrm{O}}_2$ are explained as $3l\sigma$ Rydberg states belonging to the series converging to the recently reported ∼24-eV ${}_{}{}^2{}_{}{}^{}\Pi _u^{}{}_{}{}^{}$ state of ${\mathrm{O}}_2^{+}$. Some ${\mathrm{O}}_2^{-}$ resonances related to these Rydberg states are observed with an electronic affinity of ∼0.5 eV. Numerous other structures, also appearing from 12.06 to 18 eV, originate from direct ionization and unresolved vibration of autoionizing states.