State Configuration Interaction Research Articles

Exciton States and Optical Spectra in Linear Molecular Crystals

Configuration interaction of many Frenkel exciton bands and charge-transfer states is carried out exactly. Based on the exact solution of the problem, the optical spectra is discussed. If the monomolecular optical transition is allowed, the intensities of exact exciton states are borrowed from the Frenkel excitons. Within the borrowed intensity approximation, resonance peaks and antiresonance dips in the continuum band are expected to appear depending on the magnitude of parameters. Although locations of resonances are independent of the orientation of the light polarization vector, positions and numbers of antiresonances do depend on it. Total number of antiresonances is at most one less than the number of Frenkel exciton bands. In the absence of resonance the continuum intensity depends very strongly on the nearest-neighbor charge pair interaction energy with larger intensity for smaller interaction energy. For the discrete spectra, the intensity is mainly distributed to the number of states equal to or one more than the number of Frenkel exciton bands. The relative intensities of these lines depend on the orientation of the light polarization vector. The intensity and position of the extra line varies with the nearest-neighbor charge pair interaction energy.

Dependence of Correlation Energy upon Bond Angle: Investigation of Interactions between Nearly Degenerate Electronic Configurations

Configuration interaction of low-lying electronic states is used to investigate the molecular correlation energy as a function of bond angle. Qualitative aspects of the problem are discussed using the molecular-orbital diagrams of Walsh and Mulliken. Results of configuration-interaction calculations of BeH2 and NO2+ are reported. The possibility of double minima in the potential surfaces for AB2 molecules is considered.

Vibronic effects on electron resonance spectra: the alkyl cyclooctatetraene anions

Configuration interaction, vibronic coupling and thermal population of excited states are all expected to occur in the alkyl cyclooctatetraene anions. The importance of these effects in determining the electron resonance spectra of these species is investigated theoretically and the results compared with experiment. It is concluded that vibronic coupling plays an important role.

Note on the Exchange Polarization and In-Out Effect

To investigate the correlation of electrons in the same shell due to the exchange correlation with the other unpaired electron, and so-called in-out effect, several approximate methods (Hartree-Fock, unrestricted Hartree-Fock, projected unrestricted Hartree-Fock, split shell and spin degenerate state configuration interaction) are developed. As the simplest example, the ground state 2 S and first excited state 2 P of the Li atom are considered. Slater type 1s, 2s, and 2p orbitals are adopted and the wave functions and total energies are determined by the variational method. The electron spin density at the nucleus (ψ 2 (0)) is given for the respective cases. Discussions on the results are given.