Krypton Monofluoride and Its Positive Ion

Abstract

Nonempirical quantum mechanical calculations have been carried out on KrF and KrF+. A large basis set of Slater functions was used, and the self-consistent-field (SCF) total energies for both diatomics are estimated to lie no more than 0.005 hartree above the exact nonrelativistic Hartree—Fock energies. The KrF SCF potential curve is repulsive and dissociates smoothly to Kr+F atoms. The KrF+ potential curve displays a minimum at 1.68 Å and spectroscopic constants De=−0.02 eV, and ω e=810 cm−1. The importance of polarization functions (d and f orbitals) in the single configuration wavefunctions is discussed. Electron correlation in both molecules has been investigated using first-order wavefunctions, which have yielded dissociation energies in excellent agreement with experiment for several smaller diatomic molecules. A 158-configuration correlated wavefunction predicts a flatter but nevertheless repulsive potential curve for KrF. We conclude that, except for the van der Waals interaction, KrF is unlikely to exist in the gas phase. The relation between this work and the observation of the KrF ESR in crystals of KrF2 is discussed. First-order wavefunctions containing 210 configurations for KrF+ yield the following predictions: re=1.75 Å, D0=1.90 eV, ω e=621 cm−1. Chupka and Berkowitz report the experimental value D0≥1.58 eV for KrF+. Several molecular properties are predicted for KrF+.