Theoretical study of the electronic spectrum of antimony oxide employing relativistic effective core potentials

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Abstract
Potential energy curves and electric dipole transition moments between different electronic states are computed for the antimony oxide molecule employing a relativistic configuration interaction scheme including the spin–orbit coupling interaction. Comparison is made with available experimental data as well as with the corresponding results which were recently reported for the isovalent BiO. A full core relativistic effective core potential proves to be quite effective in describing the antimony inner shells, thereby reducing the amount of computations considerably relative to an all-electron CI treatment. The calculated bond lengths re for the X1 2Π1/2 ground state and C 2Σ−1/2 excited state agree to within 0.01 Å of the respective measured values and good agreement is also found for the vibrational frequencies ωe of a large number of SbO states. The theoretical treatment tends to underestimate transition energy Te values, typically by 1000–2000 cm−1, reflecting the fact that all excited states have more open shells in their leading configurations than does the ground state itself. On the basis of the present calculations it has been possible to confirm a number of earlier assignments for the SbO upper states and also to aid in the experimental detection of several new transitions involving various a 4Π and b 4Σ− species which were not known at the time this work was begun. Theoretical values for the radiative lifetimes of the v′=0 levels of each of the above electronic states have also been obtained, and they are found to agree within at least a factor of 2 in most cases with the recent experimental values obtained by Fink, Shestakov, and co-workers. The lone exception found to date is for the B 2Σ+ state, but it is noted that nonadiabatic interactions between it and the b1 4Σ−1/2 state, as already discussed in an earlier review by Rai and Rai, could be at least partially responsible for this result.