VIBRONIC STRUCTURE OF THE CO2- REINVESTIGATION OF THE ANTISYMMETRIC STRETCH VIBRATION IN THE (X)OVER-TILDE, (A)OVER-TILDE, AND (B)OVER-TILDE STATES( ION )

We review the literature regarding v(3) excitation in the CO2+ ion and present a consistent scheme of vibronic assignments involving v(3) an d 2v(3) in the ($) over cap A(2) Pi(u)-($) over cap X(2) Pi(g) and ($) over cap B-2 Sigma(u)(+)-($) over cap X(2) Pi(g) bands. A key new pie ce of information enabling this reanalysis is provided by LIF detectio n of several ($) over cap A(v(1)02)(2) Pi(u)-($) over cap X(000)(2) Pi (g) absorption bands which are not observed in emission spectroscopy. We combine this information with previous measurements of the ($) over cap A(v(1)0v(3))(2) Pi level structure. We also carry out a rotationa l analysis of the ($) over cap A(202)(2) Pi(u)-($) over cap X(000)(2) Pi(g) band and identify a number of previously misassigned bands as ar ising from ($) over cap A(v(1)00)(2) Pi(u)-($) over cap X(v(1)02)(2) P i(g) transitions. Precise molecular constants for the X(002)(2) Pi(g) level are obtained from a recent ($) over cap A(000)(2) Pi(u)-($) over cap X(002)(2) Pi(g) emission spectrum recorded using a Fourier transf orm spectrometer. Finally, identification of the ($) over cap B(001)(2 ) Sigma(g)(+)-($) over cap X(001)(2) Pi(g) and ($) over cap B(002)(2) Pi(g) bands in the (CO2+)-C-12 and (CO2+)-C-13 emission spectra allows accurate determination of the antisymmetric stretch frequency of the ($) over cap B state. The v(3) values for ($) over cap A and ($) over cap B states thus obtained are 2685.3 cm(-1) and 1867 cm(-1), respecti vely.