Shin-ichiro Nagasaka

Polarization Dependence of Absorption and Luminescence Spectra of a 1,5-Dihydroxyanthraquinone Single Crystal

A study has been made on the polarization dependence of absorption and luminescence spectra of a 1,5-dihydroxyanthraquinone single crystal with the thickness of 0.5 mm, which was prepared by gas ph...

Coupling Between Electrons and Molecular Vibrations of an Anthracene Single Molecule in a Cyclodextrin

Optical studies of a single anthracene molecule succeeded by using a β-cyclodextrin (CyD) as an isolating cage. The absorption and the fluorescence spectra consist of several vibronic lines with 0.174–0.178 eV intervals and are mirror image with each other. In addition, their line shapes vary scarcely between RT and 2 K. These facts indicate that the anthracene molecule is almost free in the β-CyD cage. These spectra are theoretically analyzed by a free-molecule-model in which the electronic excited state couples with the vibrations \(\hbar \omega\) of the molecule with coupling strength s (Haung Rhys factor). Observed spectra are in good agreement with theoretical ones with s =1.56 and \(\hbar \omega=0.178\) eV. For the single crystal of anthracene, absorption and fluorescence were also measured. At 2 K, the zero-phonon peak becomes enhanced and the phonon lines becomes sharpened compared with the single molecule case. But at RT, the fluorescence spectrum becomes quite diffused shape. These facts suggest...

Luminescences of Pyrene Single Crystal and Pyrene Molecules Inserted in a Molecular Vessel of Cyclodextrin

Highly purified single crystals of pyrene were made by a gas phase crystal growth method from 180 times of zone-refined pyrene. The dry powder of β-cyclodextrin including a pyrene single molecule a...

Cluster Investigations in Cyclodextrin Inclusion Compounds: Theory and Experiment

Currently there is much interest in the electronic states and structural conformations of inclusion compounds as well as cluster configurations and the photochemical reactions of included molecules in such systems. The inclusion compounds of anthracene and tin tetraiodine molecules in a cyclodextrin will be discussed in detail. The most favoured configuration of the two neutral anthracene molecules inside a cylindrical molecule of γ-cyclodextrin is a face-to-face (coplanar, S-shaped) configuration which is distinguished from the gas phase, where anthracenes form a face-to-edge (T-shaped) configuration. Excitation with light (350–400 nm) forms intermolecular bonds between two anthracenes in a γ-cyclodextrin. The ab initio calculation and molecular dynamics simulation reveal that the most probable bonds are formed between the 9 and 9′ and also between the 10 and 10′ sites.

Optical properties of a 2,6-dihydroxyanthraquinone single crystal

A study has been made on the polarization dependence and the temperature dependence of absorption and luminescence spectra of a 2,6-dihydroxyanthraquinone single crystal. The single crystal structure has been investigated by X-ray diffraction and is assigned as monoclinic and the space group P21/c (#14). Electronic energy levels were calculated by molecular orbital calculation program of WinMOPAC. The absorption band at 3.2eV and the luminescence band at 2.2eV are assigned mainly to the transition between HOMO and LUMO states. The anisotropic effect on the absorption and luminescence was analyzed in view of the crystal structure. The polarization dependence is consistently explained by the direction of transition dipole moment of 2,6-dihydroxyanthraquinone molecule.

Phonon-Sideband Structures in Absorption and Emission Spectra of Organic Molecule Oligomers (N=2-6)

Phonon-sideband structures in absorption and emission spectra of oligomers are investigated using a theoretical model: A Frenkel exciton (or molecular excitation) moves among molecules of oligomers...