COLLISIONS OF LONG-LIVED EXCITED IONS OF OXYGEN AND NITROGEN

Abstract

The role of some excited ions in laboratory ion–molecule reactions has been investigated, and their possible importance in the upper atmosphere considered. The mass spectrometer techniques of Aston banding and of comparing I.P. curves of parent and product ions have been applied to studies of collision-induced dissociation and charge exchange of oxygen and nitrogen in their parent gas. In every case studied, cross sections depended markedly upon the presence in the ion beam of ions in metastable or long-lived radiative states. In order that an ion reach the collision region, it had to have a mean lifetime greater than 3 μsec.The a ⁴Π_u and b ⁴Σ_g excited states of O₂⁺ were identified in the collision[Formula: see text]Higher states of O₂⁺, which have not as yet been identified spectroscopically, were found in the collision[Formula: see text]The thresholds of these new states are 23.9, 27.9, 31.3, and 34.1 eV with an uncertainty ±0.2 eV. From the collision-induced dissociation of N₂⁺, the A ²Π_u and the [Formula: see text] states have been identified. Also, the reported transfer of the ν = 3 level of the B [Formula: see text] to the ν = 14 level of the A ²Π_u was found.The cross section for 10/01 charged exchange of N₂⁺ in N₂ exhibited a marked decrease as excited-state ions diluted the beam. The 10/01 collisions of N⁺ in N₂ and O⁺ in O₂ exhibited an increase in cross section as metastables were added to the parent ion beam. The 10/20 reaction of O₂⁺ in O₂ was also observed to depend on excited O₂⁺ ions.