Drift tube and beam studies of reactions of Ar2+ with N2

Abstract The rate constants for Ar 2+ ( 3 P ) and Ar 2+ ( 1 S ) consumption in N 2 , have been measured in a drift tube and were found to be large (close to the Langevin limit) and energy-independent up to ∼3 eV collision energy. Total Ar 2+ ( 3 P ) reaction cross-sections in good agreement with these results were measured in a beam attenuation experiment in the eV-collision energy regime, which also showed that only 2% (0.4 A 2 ) of the reaction is due to single charge transfer, giving Ar + (+N + 2 ). Measurements of the translational energy distribution of Ar + revealed that these species originate with center-of-mass Coulomb repulsion energies of 4—5 eV, the energy balance suggesting formation of electronically excited N 2 + . Observation of optical emission from the Ar 2+ + N 2 collisions corroborated this. Spectra taken in the 2000—5000-A range and analyzed using computer simulation identified N + 2 ( D 2 Φ g ) as one of the emitting states. The total N 2 + luminescence cross-section is about 0.20—0.30 A 2 , thus constituting a large fraction of the total N + 2 , formation cross-section.