摘要:

Absorption and emission spectra of the title oligothiophenes, both in chloroform solution and as solid (or in PMMA ss), are given. Evidence is found for the simultaneous existence of various conformers that differ markedly in their conjugation lengths.

ISSN:1058-725X    

DOI:10.1080/10587259208047006

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Singlet excitation energy transfer processes and inter-system crossing in the mixed crystalline systems, p-terphenyl: :tetracene, p-terphenyl:pentacene and benzoic acid:pentacene were investigated in the temperature range 2 - 300 K using stationary fluorescence spectroscopy.

ISSN:1058-725X    

DOI:10.1080/10587259208047007

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The optical absorption line shape of a polymeric chain under the influence of conformational disorder is investigated. In the model consecutive segments of the polymer chain are allowed to be randomly oriented in space. Intrinsic disorder is taken into account phenomenologically in the Green's function of the chain. A comparison shows that the contribution of conformational disorder on the line width may be considerable.

ISSN:1058-725X    

DOI:10.1080/10587259208047008

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

For a model dimer the influence of vibrational degrees of freedom on electronic excitations is described by a dichotomic Markov process with coloured noise. Within this model the energy transport between the two units of the dimer, especially the transition between coherent and incoherent motion is discussed. Furthermore the optical absorption line shape is evaluated for various values of the model parameters.

ISSN:1058-725X    

DOI:10.1080/10587259208047009

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We report the picosecond time resolved spectra of the optical Stark effect on a quasi-two-dimensional exciton localized at a stacking fault plane in Bil3crystals. The ultrafast response of the blue-shift due to the optical Stark effect(OSE) is confirmed in picosecond time domain under negative detuning excitation condition. For positive detuning excitation, an ultrafast switching from the red shift by the OSE to the blue-shift due to the nonlinear interaction with the large amount of incoherent “real” exciton occurs. Under the just resonance excitation, the blue-shift due to the “real” exciton is also observed during several tens of picoseconds after the pumping, and an absorption bleaching occurs at the timing of the pump-pulse peak. The bleaching is discussed in connection with the OSE.

ISSN:1058-725X    

DOI:10.1080/10587259208047010

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An exciton confined at a two-dimensional stacking fault in Bi13 crystal reveals large optical nonlinearity and ultra fast response for high density excitation. It shows three resonant luminescences whose decay-time constants are 20ps, 40ps and 900ps from the higher energy states reflecting cascade-type relaxation processes. By the degenerate four-wave mixing (DFWM) measurements, the dephasing times of three exciton states were obtained as 8.6ps, 15ps and 34ps. The dephasing at the lowest state is governed mainly by the LA-phonon intra-band scattering. While, at the higher states, it is governed by the cascade relaxation to the lower states in addition to the phonon scattering. It is found that the dephasing is also influenced by the exciton-exciton scattering under the high density excitation. A nonlinear transition involving a multi-photon process is observed in the excitation response of the DFWM signal. This result suggests the existance of the excitonic molecule.

ISSN:1058-725X    

DOI:10.1080/10587259208047011

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Absorption line series WJ(J=I,II,III,…) appeared below the indirect, edge in BiI3has been studied. The series is assigned to the excitons confined in mesoscopic domains produced by deformation faults characteristic of layered materials. Each line consists of four structures which correspond to x+iy, x-iy, z, and pure triplet states originated from the bulk cationic excitons. The energy separations between these four states are depend on the size of mesoscopic domains in which an exciton is confined. By introducing a disk-like shape model of the mesoscopic domain, the experimental results are analyzed on the basis of anisotropic quantum size effects on the cationic excitons. The relative motion of the exciton is found to be strongly affected by the localization of the translational motion in the direction perpendicular to the confinement axis.

ISSN:1058-725X    

DOI:10.1080/10587259208047012

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We have observed novel photo-induced phenomena in conjugated polymers; the reversibly photo-induced phase transitions in single crystals of poly-diacetylene(PDA). Dependence of the phase conversion efficiency on excitation photon energy shows that the photo-generation of charge-carriers (polarons), not excitons, is responsible for the macroscopic phase change.

ISSN:1058-725X    

DOI:10.1080/10587259208047013

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We observed that (1) the luminescence spectra of α-perylene shifted by 440 cm-1as much as the change in the excitation photon energy, from 22100 cm-1(452.5 nm) to 22540 cm-1(443.7 nm), whereas the luminescence spectrum of pyrene shifted by 100 cm-1according as the excitation photon energy in an energy region from 26940 cm (371.2nm) to 26730cm-1(374.1nm), (2) for pyrene microcrystals the luminescence decay under resonant excitation increased as the excitation energy increased, (3) in both materials intense fsee-exciton luminescence was observed but self-trapped exciton luminescence was not.

ISSN:1058-725X    

DOI:10.1080/10587259208047014

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Absorption spectra are reported for sodium clusters incorporated into cages of zeolite LTA crystals, where the expected cluster diameter is about 11 Å at maximum. The spectra exhibit the bands originated from the excitation of the quantum-confined electron-hole pair as well as the surface plasmon excitation.

ISSN:1058-725X    

DOI:10.1080/10587259208047015

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor