15min:

L. CHEN, D. E. WOON AND T. H. DUNNING JR., Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

Following studies of the nature of covalent and recoupled pair bonding in PF_n( n =1-5), SF_n( n =1-6), and ClF_n( n =1-7), we have used the recoupled pair bonding model to investigate the ClF_n^+/-( n =1-5) ions. The behavior of the cation series parallels the SF_n series to great extent, while the behavior of the anion series would parallel that of ArF_n if those species were bound. In the present research, we predict experimentally measurable properties, such as the electron affinities (EA) and ionization energies (IE) of the associated neutral ClF_n species. The optimized ground state structures, bond energies, and spectral properties of ClF_n^+/- were obtained by employing high level ab initio calculations (MRCI, CCSD(T)) with correlation consistent basis sets. Our predictions agree well with the structures of experimentally observed species, including ClF₂⁺, ClF₂^-, ClF₄⁺, and ClF₄^-. Low-lying excited states of ClF⁺(^{4 -}) and ClF₂⁺(³B₁), were also identified. We found the excited ³B₁ state of ClF₂⁺ is bent with an angle of 154.8^\circ and a bond length of 1.596 Å at the RCCSD(T)/AVQZ level. We also found a major difference between SF₂ and ClF₂⁺: the ³A₂ state of SF₂ is bound while the same state of ClF₂⁺ is repulsive. Second, we systematically explored the bond formation processes, adding F atoms one at a time to the optimized ClF_n^+/-(1\leq n \leq5) ions. We found the ionization energies and the electronic affinities both exhibit an oscillating trend as seen in the bond energies of the neutral ClF_n species. The structural and energetic data obtained by our calculations might help spectroscopists to identify new ClF_n^+/- species or to detect new electronic states of known species.