Relativistic Effects in the Electronic Structure of Atoms.

Periodic trends in relativistic effects are investigated from H through Lr using Dirac-Hartree-Fock and nonrelativistic Hartree-Fock calculations. Except for Pd (4d) (5s), all atoms have as outermost shell the ns or n'p spinors/orbitals. We have compared the relativistic spinor energies with the corresponding nonrelativistic orbital energies.

Cu 4s → 4p atomic like excitations in the Ne matrix.

The lowest three or four excited states (the triplet or quartet states) of the Cu atom in a neon (Ne) matrix have been studied experimentally, and have been presumed to have the electronic configuration of Cu 4p(1). The origins of the triplet and the quartet are not yet fully clear, although many models have been proposed. It has been argued, for example, that the existence of different trapping sites would give rise to two partly overlapping triplets, leading to spectra having three or four lines or more.

Characterization of molecular orbitals by counting nodal regions.

The number of nodal regions can be used as an index for characterizing molecular orbitals. A computer program has been developed to count the number of nodal regions, based on the labeling and contraction algorithms. This program is applied to the water molecule, the hydrogen sulfide molecule, the hydrogen atomic orbitals, the Rydberg excited states of ethylene, dissociation of carbon monoxide, and CASSCF calculations of formaldehyde.