A computational study of metastable states of CO2+.

Extensive calculations of energies and lifetimes of vibronic and rovibronic states of the CO(2+) dication are performed using the electronic energy potentials and spin-orbit couplings published recently by Sedivcova et al. [J. Chem. Phys. 124, 214303 (2006)] and by Eland et al. [J. Phys. B 37, 3197 (2004)]. Siegert quantization, bound-continuum configuration mixing, two-potential, and semiclassical methods are exploited in the calculations. Lifetimes for predissociation and tunneling, varying over a wide range, are determined, demonstrating a very good agreement between results yielded by the different methods. Dependence of the calculated predissociation characteristics (level widths and shifts) on the individual potentials and couplings is analyzed. The potentials of Sedivcova et al., especially the repulsive potential of the (3)Sigma(-) state, are found insufficiently accurate in the medium range of the internuclear distance to be useful in simulations of the decay of the lowest vibronic states of the ion, X (3)Pi(v = 0,1) and a (1)Sigma(+)(v = 0,1). Combining the potentials of Eland et al. with the SO couplings of Sedivcova et al. is demonstrated to provide the best description of metastability of the ion so far. Purely vibronic models constructed in this way give lifetimes in a reasonable agreement with all existing experimental values and estimates. The largest deviations, tau(expt)/tau(calc) approximately 20, occur in the X (3)Pi(v = 1,2) cases. Strong evidence is provided that accounting for rotational motion of nuclei, spin-uncoupling perturbations, and diagonal spin-orbit couplings can reduce these deviations substantially, approximately ten times. The predissociation lifetimes of the rovibronic states A (3)Sigma(0,1)(+)(Jv) are predicted to be, with no exception, more than 100 times shorter than radiative lifetimes of these states.