SPIN-ORBIT COUPLED EXCITED-STATES IN TRANSITION-METAL COMPLEXES - A CONFIGURATION-INTERACTION TREATMENT OF HCO(CO)(4)

A direct spin-orbit coupled configuration interaction method is presen ted. The basis functions are Slater determinants expressed as combinat ions of alpha and beta strings. The one and two electron operators are expressed in second quantization form. Spin-orbit coupling is describ ed as a one electron effective operator. The structure of the configur ation expansion is single and double excitations from a limited full C I space. Calculations of the M(s)=0 component of the three lowest exci ted states (1,3)E and (3)A(1) in HCo(CO)(4) have been performed in ord er to evaluate the spin-orbit interactions responsible for the (1)E--> (3)E and the (1)E-->(3)A(1) radiationless transitions. A large differe nce is found in favor of the (1)E-->(3)E path.