P. Jeffrey Hay

Configuration interaction studies of O3 and O+3. Ground and excited states

We report the results of extensive configuration interaction calculations (double ζ basis) on the ground and 15 excited states of ozone and the eight lowest states of the ozone positive ion. The studies on ozone are carried out as a function of both bond length and bond angle. We find that three excited states of ozone may be bound with respect to the ground states of O2 and O. Additional information is provided on the ring state (60 ° bond angle) previously reported. Two of the excited states of ozone are known spectroscopically and the ionization potentials of the first three states of O+3 are now known experimentally. These experimental results are in good agreement with the theoretical calculations.

Relativistic effects in ab initio effective core potentials for molecular calculations. Applications to the uranium atom

The procedure of deriving ab initio effective core potentials (ECP) to incorporate the Coulomb and exchange effects as well as orthogonality constraints from the inner core electrons is extended to include the dominant relativistic effects on the valence orbitals. An ab initio approach is then described which enables the valence electrons in heavy atoms to be treated in a standard nonrelativistic manner by including the effect of the relativistic core–valence interactions directly into the ECP. The starting point for this procedure is the Pauli Hartree–Fock relativistic treatment of Cowan and Griffin. The pseudo‐orbital transformation and derivation of the l‐dependent effective core potentials are analogous to the nonrelativistic case with certain modifications. Analytic forms for the pseudo‐orbitals and ECP’s are derived for the U atom, and results of valence electron calculations are presented.

Theoretical evidence for bound electronic excited states of ozone

Abstract Extensive configuration interaction calculations (up to 1532 spin eigenfunctions) have been carried out on ozone with both minimal and extended bases. Vertical and adiabatic excitation energies to 14 excited states are reported, including seven states with vertical excitation energies less than 4 eV. Our calculations indicate that in addition to the ground state there are four other states of ozone ( 3 B 2 , 3 A 2 , 1 A 2 and 3 B 1 ) bound with respect to dissociation to ground state O 2 and O (by 0.4, 0.3, 0.1 and 0.0 eV, respectively). With such small bonding energies, the current results cannot be said to show definitively (except perhaps for 3 B 2 ) these four states to be bound with respect to O 2 + O. However, the theoretical evidence is sufficiently strong as to warrant careful experimental studies. Such bound excited electronic states could play important roles in the chemistry of the upper atmosphere and in the chemistry of oxygen discharge systems. One (or more) of these states may be responsible for the short-lived intermediate (‘ozone precursor’) recently observed in oxygen radiolysis.

The effect of symmetry restrictions upon the hyperfine properties

The effect of spatial symmetry restrictions upon the calculated values of the hyperfine splitting constants is examined and results are reported for B, C, O and F. It is found that, if no symmetry restrictions are placed upon the unrestricted Hartree-Fock orbitals, the resulting hyperfine constants (except spin densities) are in good agreement with experiment and with configuration interaction calculations. Nuclear magnetic moments and quadrupole moments are reported on the basis of these calculations and the observed hyperfine structure.