Masayoshi Nakano

Exciton migration dynamics in a dendritic molecular aggregate

Abstract We investigate exciton migration dynamics in two types of dendritic molecular aggregate models, i.e., Bethe lattice, with mutually distinct intermolecular interaction between adjacent linear legs at the branching points. Each monomer molecule is assumed to be a dipole unit (a two-state model) coupled with each other by the dipole–dipole interaction. The generation of one exciton in the aggregates by the incident laser field and its subsequent dynamical behavior are investigated in a numerically exact manner. The two types of models show different exciton energy structures and distribution. It is also found that relaxation effects in the exciton states are essential for exciton migration from the periphery to the core.

Third-order nonlinear optical properties of fractal- and nonfractal-structured oligomers modeled after dendron parts in Cayley-tree-type dendrimers

As an extension of our previous study on polarizabilities [J. Chem. Phys. 115, 1052 (2001)], we investigate the molecular third-order nonlinear optical properties, i.e., the second hyperpolarizabilities (γ), of three types of model oligomers (made of phenylene vinylenes), i.e., para-oligomers and meta-oligomers with fractal and nonfractal structures, which are considered to be models of dendron parts involved in Cayley-tree-type dendrimers. Similarly to the polarizability case, the chain-length dependence of γ of para-oligomers is found to be much larger than that of nonfractal meta-oligomers, while fractal meta-oligomers exhibit an intermediate chain-length dependency of γ between them. The spatial contributions of π-electrons to γ of these systems are elucidated using hyperpolarizability density analysis. It is found that the spatial contributions of π-electrons to γ of nonfractal meta-oligomers are much smaller than those of para-oligomers and are well decoupled at the meta-substituted benzene rings, w...

Intermolecular-interaction effects on quantum-phase and information-entropy dynamics of dimers interacting with a single-mode coherent field

Abstract Using a numerically exact approach to the dynamics of a molecule–photon field-coupled system, we investigate the quantum-phase and the information-entropy dynamics of molecular dimers interacting with a single-mode coherent photon field. The intermolecular interaction between monomers is treated by the dipole–dipole interaction. The influence of the dipole–dipole interaction on the feature of the collapse–revival behavior of dimer population is revealed from the viewpoint of the photon-phase dynamics and the entanglement between dimer and photon.

Exciton Migration Dynamics of D58-like Dendritic Molecular Aggregate

Abstract We report the exciton population dynamics of D58-like dendritic molecular-aggregate model involving chromophores at the position of acetylene units of a phenylacetylene dendrimer D58. It is found that the relaxation effect is essential for exciton migration from the periphery to the core.

Theoretical study on the off-resonant polarizabilities of linear, square-lattice and dendritic molecular aggregates

We investigate the intermolecular-interaction effects on the off-resonant polarizabilities (a) of fractal-dimensional (dendritic), one-dimensional (linear) and two-dimensional (square-lattice) aggregate models in order to elucidate the structure-property relation in a. As a fractal-dimensional system, we consider a D25-like dendritic molecular-aggregate model, which involves chromophores at the position of acetylene units of a phenylacetylene dendrimer D25. It is found for a dendritic aggregate that intermolecular-interaction effects more enhance the contribution to a in the core region than that in the periphery region.

Theoretical study on the near-resonant second hyperpolarizability (γ) of a dendritic molecular aggregate : the spatial contribution of intermolecular-interaction and relaxation to γ

Second hyperpolarizability (γ) of a dendritic molecular aggregate (D25) in the resonant region is calculated using a two-exciton coupled-dipole model. Using a visualization method of exciton generation to y, there is found to be a significant difference in the spatial contribution between intermolecular-interaction and relaxation effects on γ, which is dramatically changed compared to the case of the dendritic aggregate without intermolecular-interaction.

Exciton Condensate in Model Dendrimers

Abstract We calculate the time evolution of excition density in a model dendrimer. Possible models with dendrimers for exciton condensates are proposed.

Polarizabilities of Dendritic Molecular Aggregates: Contribution of Exciton Generation

Abstract The spatial contributions of exciton generation to polarizabilities (α) are elucidated for two types of molecular aggregate models with a dendritic structure, one of which involves a different type of dipole units such as transition metal compounds.

Exciton Migration Pathways in Dendritic Molecular Aggregates

Abstract The energies and transition moments of exciton states for dendritic molecular aggregates are calculated using a model Hamiltonian involving dipole-dipole interaction. Exciton pathways are found to be remarkably influenced by the constituent monomer units.