Dissociative recombination of N₂⁺, O₂⁺, and NO⁺: Rate coefficients for ground state and vibrationally excited ions

Abstract

We review recent advances in the study of the dissociative recombination of molecular ions with electrons with a primary emphasis on experimental studies. In particular, we focus on previous experimental measurements of recombination rates for N 2 + , O 2 + , and NO + ions. In the context of this review, we present temperature dependent rate coefficients from recent merged beam studies of the dissociative recombination of N 2 + , O 2 + , and NO + ions with electrons. Identifying underlying physical differences between the various experimental techniques enables a discussion of the effects of vibrational excitation on the dissociative recombination of these major ionospheric species of ions. For T < 1200 K, we conclude that the recombination rates for N 2 + , O 2 + , and NO + ions in the ground electronic and vibrational states respectively are 2.2 × 10 −7 (T e /300) −0.39 cm 3 s −1 , 1.95 × 10 −7 (T e /300) −0.70 cm 3 s −1 , and (3.5 ± 0.5) × 10 −7 (T e /300) −0.69 cm 3 s −1 . Vibrational excitation is shown to play a significant role in laboratory measurements of these recombination rates. For each of these species, vibrationally excited ions yielded a lower recombination rate than the ground state. We also discuss the recombination of these species of ions for T > 1200 K.