THE ELECTRONIC STRUCTURE OF SCANDIUM FLUORIDE.

The electronic structure of the low lying singlet and triplet states of Sc-F has been studied using the $P\Phi L-Cl$ approach. The ground state is calculated to have $^{1}\Sigma^{+}$ symmetry with bond length of $1.811 \AA$, a vibrational frequency of $742.3 cm^{-1}$ and an anharmonicity constant $\omega_{e}X_{e}$ of $4.1 cm^{-1}$. The bonding in this state is ionic and corresponds to $Sc^{+}F^{-}$. Using the ground state GVB orbitals the $IV\Phi$'s were constructed and configuration interaction representations as a function of internuclear separation were determined for the forty lowest electronic states of singlet and triplet symmetry. The internuclear separation and various spectroscopic constants have been calculated for each state and where possible, molecular orbital occupancies have been assigned. The results of these calculations are in reasonable agreement with the limited experimental data available (7 singlets and 5 triplets have been observed) and in addition provide considerable insight into the problems of and opportunities for the ab-initio predictions of the electronic structure of transition metal halides