Electronic states of Pt2

Complete active space MCSCF (CASSCF) followed by first-order configuration interaction (FOCI) calculations are carried out on low-lying electronic states of Pt2. The spin–orbit interaction is introduced through a relativistic configuration interaction method. Twenty-two low-lying ω–ω states with Te<15 000 cm−1 and 11 λ–s states with Te<3189 cm−1 are found. The nature of all these electronic states is discussed. The calculated Re values of all the electronic states are between 2.4 and 2.6 Å. The spin–orbit effects are found to be significant for the electronic states of Pt2. The CASSCF/FOCI dissociation energies of the strongest-bound states in the absence of spin–orbit interaction are calculated to be about 2.3 eV. The spin–orbit interaction decreases the De. The dissociation energies of the strongest-bound states in the presence of spin–orbit interaction are about 1.85–1.95 eV.