High resolution absorption spectroscopy of N+2X(v″=0)→ A(v′=4) using charge exchange detection

The optical absorption spectrum of the N+2 (4,0) Meinel band has been studied at high resolution (0.1 cm−1) using an ion flow tube in the cavity of a ring dye laser. The absorptions are observed by detecting the Ar+ products of the charge exchange reaction N+2 (A)+Ar→N2(X)+ Ar+. Improved molecular constants are obtained for the N+2A 2Πu(v=4) state. The charge exchange detection technique should prove generally useful for studying absorptions to long lived excited states.