Laser induced fluorescence from the A 2Πi(v = 0) state of CO+

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Abstract
A pulsed, tunable dye laser is used to obtain either the excitation spectrum for the A 2Πi–X 2Σ+ (0,0) band of CO+, or the time resolved fluorescence from individual rotational levels of the upper state for this transition. The ions are formed by reacting CO with helium metastable atoms produced in a dc discharge. Although the rotational structure of the A 2Πi (v = 0) state is well known from numerous studies of the emission spectra of CO+, our laser excitation spectrum reveals perturbations in this state which have not been reported previously. ’’Extra’’ lines are observed in the R21 and Q22 branches of the A 2Π1/2–X 2Σ+ (0,0) sub‐band and are associated with the e‐parity rotational levels of the A 2Π1/2 spin component having J values of 2.5, 3.5, 4.5, 5.5, 6.5, and 7.5. The perturbing levels which are the source of these ’’extra’’ lines are the e parity or F1 spin components of the X 2Σ+(v = 10) state having the same J values. Perturbation matrix elements and wave function mixing fractions are determined from the experimental data. The molecular constants of the interacting states are deduced and a discussion is given on the effect of these perturbations on the time resolved fluorescence from individual rovibronic levels of the A 2Πi(v = 0) state.