Collisions of Monoenergetic Electrons with NO2: Possible Lower Limits to Electron Affinities of O2 and NO

The yields of O−, NO−, and O2− ions produced by dissociative attachment of electrons to NO2 have been studied as a function of the electron energy from 0 to 6 eV. A modulated retarding-potential-difference technique permitted electron-energy resolution of approximately 0.1 eV. The measured appearance potentials for NO− and O2− were found to be consistent with an electron affinity of ≥0.65 eV for NO and ≥1.1 eV for O2. These lower limit measurements to the electron affinities of O2 and NO are discussed in relation to previous studies of electron attachment to these molecules.