AB-INITIO RELATIVISTIC CONFIGURATION-INTERACTION CALCULATIONS OF THE SPECTRUM OF BISMUTH OXIDE - POTENTIAL CURVES AND TRANSITION-PROBABILITIES

A series of configuration interaction calculations employing relativis tic effective core potentials including the spin-orbit interaction is reported for the X(1) (2) Pi(1/2) ground and numerous low-lying excite d states of the bismuth oxide molecule up to 30 000 cm(-1). Special di fficulties connected with the treatment of open-shell systems and doub le-group irreducible representations are discussed and a feasible comp utation scheme is developed for dealing with them. The spin-orbit inte raction is found to cause a high level of mixing between a variety of low-lying lambda-s states, producing a number of avoided crossings whi ch play a key role in determining the character of the BiO spectrum. A comparison with existing experimental data for both the energy locati ons and intensities of a large number of band systems indicates that t he present calculations are capable of predicting T-e values to an acc uracy of 0.1-0.2 eV. Corresponding radiative lifetime results generall y agree within a factor of 2, with the best experience occurring for r elatively strong transitions. The state which was originally assigned as A (2) Pi(1/2) actually turns out to be dominated by the (4) Pi lamb da-s state. The corresponding state with Omega=3/2 has recently been d iscovered by Fink and Shestakov and is found to undergo a strong nonad iabatic interaction with the X(2) (2) Pi(3/2) state. Two other related states A(3) (4) Pi(1/2) are predicted by the present calculations, bu t have not yet been verified experimentally. Similarly, the L(1) (2) P hi(7/2) and L(2) (2) Phi(5/2) states found in the present work have al so not yet been observed.