Spectroscopy of N₂⁺ Meinel bands and CO⁺ comet tail bands

The N₂⁺ [X² Σ_g ⁺(v″=0)-A ²Π_u(v′=5)] Meinel band and the CO⁺[X ²Σ⁺(v″=0)-A ²Π(v′=1,2)] comet tail bands have been measured with Doppler-limited resolution in a selected ion flow tube (SIFT) apparatus using laser induced charge transfer. The charge transfer medium was Ar, which does not react with those ions in their ground levels, but undergoes a strong charge transfer reaction with the excited states under consideration here. The use of a single mode laser and the SIFT technique led to much higher signal-to-noise than obtained in earlier work. These measurements are the first reported with Doppler-limited resolution on any of these bands, and are analyzed to provide substantially improved molecular constants for the excited states involved in the transitions.