Osamu Tanimoto

Calculation of lower excited electronic levels of benzene with the Green's function method

The Greens function method for the calculation of orbital energies which was discussed in a preceding paper is applied to the calculation of the lower excited states of the benzene molecule. The Dyson equation for the polarization (particle—hole) propagator is derived with the diagrammatic technique and the secular equation which gives poles of the polarization propagator is solved. The random phase approximation is not used in our calculation. Theoretical results are discussed in comparison with experimental data. Using a model system of two π-electrons, our method is compared with the equations-of-motion method.

Calculation of orbital energies in π-electron systems with the Green's function method

A general method for treating orbital energies of π-electron systems is proposed in the present paper. This method is based on the application of a diagrammatic technique to N-Fermion (not infinite) systems. Higher-order terms in the perturbation series are systematically evaluated and the effects of correlation on the orbital energies are obtained. Applications to the ethylene and cyclobutadiene molecules are discussed.

Simulations on soliton dynamics in polyacetylene systems

Abstract Simulations on soliton dynamics in polyacetylene (PAC) systems are carried out based on an improved SSH model. The results show that the threshold for stability of soliton dynamics in PAC is not so high. We also investigate the soliton dynamics in the presence of a charged dopant. Simulations of the soliton dynamics in an external electric field show that the effective inertial mass of a soliton is very large. This is due to soliton-phonon couplings.

DYSON-TYPE BOSON MAPPING FOR THE ELECTRON EXCITATION PROBLEM IN MOLECULES

Abstract Electron excitation energies of low lying excited states in molecules are discussed with reference to the Dyson-type boson mapping method. In spite of the lack of unitarity, this method is useful for describing the collective motion of particle-hole pairs, because a particle-hole pair operator mapped on the Dyson-type boson space is composed of a finite power series of boson operators and it has been shown that it is possible to make the eigenvalue problem hermitian (K. Takada, Nucl. Phys. A, 439 (1985) 489; Phys. Rev. C, 34 (1986) 750). In the present paper, we discuss how to map the operators in the fermion space onto the Dyson-type boson space. We obtained the Dyson-type boson Hamiltonian in order to discuss the electron excitation energies in molecules.