Accurateabinitiopotential curves for theXthinsp;2Pgr;g,Athinsp;2Pgr;u,athinsp;4Sgr;minus;u, and2Sgr;minus;ustates of the 0minus;2ion

摘要

Abinitiopotential energy curves and spectrocopic constants of theXthinsp;2Pgr;g,Athinsp;2Pgr;u,athinsp;4Sgr;minus;uand2Sgr;minus;uof the negative ion of molecular oxygen (0minus;2), of major interest in the upper atmosphere, are presented in a sequence of increasing computational sophistication. The unique features of the correlation problem for homonuclear ions are analyzed in detail. The most accurate 76hyphen;configuration MCSCF groundXthinsp;2Pgr;gstate results are examined and found (as expected) to be in excellent agreement with experiment. The most accurateAthinsp;2Pgr;uexcited state results (also involving a 76hyphen;configuration MCSCF wavefunction) are expected to be of comparable accuracy, while somewhat less accuracy is expected for the best calculations of the4Sgr;minus;uand2Sgr;minus;ustates (64 and 65 configurations used, respectively).