AKAI Ichiro

©2018 The Physical Society of Japan. We propose a new method for the analysis of extended X-ray absorption fine structures (EXAFSs), by the application of sparse modeling using simplified basis functions based on the single-scattering approximatio...

? 2017 Author(s). By Bayesian inference with Metropolis algorithm, we have succeeded highly accurate estimation of a vibrational frequency as well as an initial phase for a damped oscillation contained in coherent phonon signals. Although a rise a...

? 2015 Elsevier B.V. Abstract We investigated biaxial stress effects on the yellow 1S ortho excitons in Cu < inf > 2 < /inf > O thin films recrystallized between paired MgO plates by measuring photoluminescence spectra, X-ray diffraction and polar...

? 2014 The Physical Society of Japan. We investigated the stress effects on nP yellow excitons in Cu 2 O thin films recrystallized epitaxially in a sample gap between paired MgO substrates. In such samples, it is expected that a two-dimensional co...

We have investigated stress effects on yellow exciton states in a Cu 2 O thin film sandwiched by MgO plates by measuring wavelength modulated (WM) absorption spectra and their thermal variations. In the WM absorption spectra, dispersive spectral s...

In order to clarify uniaxial stress effects on a green excitonic series in Cu 2 O, we measured temperature dependence of wavelength modulated (WM) absorption spectra of a Cu 2 O thin film sandwiched by MgO plates. In these spectra, excitonic reson...

We investigated high density excitation effects in propagation and diffusion processes of free excitons confined in an L z -gradient GaAs quantum well (QW). From measurements of μPL spectra, it was found that driving force owing to a confined-ener...

We developed a newly designed wavelength modulation (WM) system for highly sensitive absorption spectroscopy. In our system, the WM is realized by yawing an output mirror in a monochromator. In order to control an amplitude Δλ of the WM in a wide ...

We investigated temperature dependence of wavelength modulated (WM) absorptionspectra for studying stress effects on a Cu2O thin film. In these spectra, 2P?4P spectralstructures can be clearly detected in both yellow and green excitons even at 180...

Excitons, photocarriers, and bias-induced carriers in regioregular poly(3-alkylthiophene) (P3AT) films were investigated using a variety of spectroscopic techniques, such as continuous-wave- (cw-) and femtosecond (fs-) transient photoinduced absor...

Synthetic supermolecules such as π -conjugated light-harvesting dendrimers efficiently harvest energy from sunlight, which is of significant importance for the global energy problem. Key to their success is rapid transport of electronic excitation...

From analyses of molecular vibrations, we have studied rapid energy transfer (ET) process in a series of star-shaped stilbenoid phthalocyanines (SSSnPc;n=1,2) having π-conjugated light harvesting antennas. In SSSnPc, the highly efficient ET occurs...

We investigated rapid energy transfer (ET) processes in dendrimers having meta -linked branching light harvesting antennas. It was found that, at room temperature (RT), the rapid ET occurs efficiently from the antennas to the core and gives rise t...

We have performed spectroscopic measurements combining with the diode operation of [6,6]-phenyl C61 butyric acid methyl ester (PCBM) for directly characterizing the nature of its n -carriers. The measurements in the visible region reveal that elec...

We investigated rapid energy transfer (ET) processes in dendrimers having meta-linked branching light harvesting antennas. It was found that, at room temperature (RT), the rapid ET occurs efficiently from the antennas to the core and gives rise to...

Rapid energy transfer dynamics in light-harvesting small dendrimers (star-shaped stilbenoid phthalocyanine: SSS2Pc-m, m=1,2) having different numbers of oligo(p-phenylenevinylene) periphery antennas was studied by time-frequency two-dimensional (2...

Bleaching probe spectroscopy performed for regioregular poly(3-hexylthiophene) diodes reveals that coexistent morphological phases determine the conducting and optical properties of conjugated polymer films. Photoinduced absorption measurements de...

Temperature dependences (4-300 K) of photoluminescence (PL) and absorption spectra of 16-mer oligothiophene (16 T) extremely diluted in polypropylene (PP) have been investigated in order to clarify temperature effects on quasi-isolated conjugated ...

Decay kinetics of the luminescence of Ag - centers doped in NaCl, KBr, and CsBr single crystals have been investigated in the temperature range from 4 K to 260 K. At low temperature, the radiative transitions from the 1 T 1u states in the Ag - ...

The temperature dependence (4 K-300 K) of the photoluminescence (PL) and absorption spectra of 16-mer oligothiophene (16T) diluted in polypropylene (PP) with a weight ratio of 1/30000 has been investigated in order to clarify the intrinsic tempera...

We investigate a rapid energy transfer (ET) process and its temperature dependence in a star-shaped stilbenoid phthalocyanine (SSS1Pc) dendrrimer having πconjugated light-harvesting (LH) antennas. In SSS1Pc, intense core-photoluminescence is obser...

We investigate a rapid energy transfer (ET) process and its temperature dependence in a star-shaped stilbenoid phthalocyanine(SSS1Pc) dendrimer having π-conjugated light-harvesting (LH) antennas. In SSS1Pc, intense corephotoluminescenceis observed...

We investigate rapid energy transfer (ET) and its temperature dependence in a star-shaped stilbenoid phthalocyanine (SSS1Pc) dendrimer having π-conjugated light-harvesting (LH) antennas, and develop an appropriate model. In SSS1Pc, an intense core...

Rapid energy transfer dynamics in light-harvesting small dendrimers (star-shaped stilbenoid phthalocyanine: SSS1-Pc) having oligo (p-phenylenevinylene) peripheries was studied by real-time pump-probe imaging spectroscopy implemented on a single-sh...

Energy transfer and shielding effect are studied in wire-type dendrimers (GnPPV: n-thgeneration dendrimer with poly(p-phenylenevinylene) backbone; n = 1, 2) havingoligophenylene light-harvesting (LH) antenna. Following the excitation of the LH-ant...

The photoluminescence (PL) dynamics of poly[2-methoxy-5-(2′-ethyl- hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) blended in host polymer (polypropylene, PP) matrix as well as that in the neat film has been studied. The concentration of MEH-PPV in th...

The effect of excitation level on the luminescence of ZnMnTe/ZnMgTe quantum-well (QW) structures has been studied. We find that result depend strongly on the QW width and manganese concentration. The increasing optical pumping implies a degradatio...

The emission spectra of Zn 1-x Mn x Te/Zn 0.6 Mg 0.4 Te and Cd 1-x Mn x Te/Cd 0.5 Mg 0.5 Te quantum-well structures with different manganese concentrations and quantum-well widths are studied at excitation power densities ranging from 10 5 to 10 7...

Luminescence properties including decay kinetics have been investigated for Ag - centres doped in NaCl single crystals in the temperature range from 7 to 250K. When the C absorption band peaking at 4.5eV is photo-excited at low temperature, the A...

The temperature dependence of excitonic energy transfer is investigated in both small and large dendrimers having meta-linked light-harvesting peripheries. In these dendrimers, highly efficient excitonic energy transfer takes place from peripherie...

Morphology dependence of excitonic energy transfer in light-harvesting dendrimers (4thmQ: m = 1, 3, and 4) with fourth branching generation is investigated from the measurements of photoluminescence (PL) spectra and the 1 H-NMR spin-spin relaxati...

Temperature dependence of the energy-transfer dynamics in a light-harvesting small dendrimer (star-shaped stilbenoid phthalocyanine: SSS1Pc) having oligo (p-phenylenevinylene) peripheries is investigated. We measured stationary and time-resolved p...

The intrinsic intrachain photoluminescence (PL) dynamics of conjugated polymers in the solid state is investigated. We focus on the PL properties of long β -substituted oligothiophenes (8-mer, 12-mer, and 16-mer) and regio-regular (RR) and regio-r...

Optical properties on the basis of absorption and photoluminescence (PL) have been examined for regioregular (RR-) poly(3-octylthiophene) (P3OT) and regiorandom (RRa-) P3OT diluted in polypropylene (PP). RR-P3OT gives blue-shifted spectra in both ...

The structure of hexanuclear 6-methyl-2-pyridinethiolato copper(I) [Cu 6 (6-mpyt) 6 ] crystals has been studied by the X-ray diffraction analysis. These crystals show highly efficient luminescence whose color changes drastically from red to green...

The energy-transfer dynamics from peripheries to cores was investigated in two series of light-harvesting small dendrimers. In a star-shaped stilbenoid phthalocyanine having π-conjugated peripheries, a highly efficient and rapid energy transfer oc...

We have investigated the photoluminescence (PL) characteristics of poly(3-octylthiophene) (P3OT) diluted in a solid matrix of polypropylene (PP). Using time-resolved PL spectroscopy, we have identified a continuous increase in PL quantum efficienc...

Heat generation caused by nonradiative relaxation processes in tris-8-hydroxyquinoline aluminum (Alq 3 ) was measured at 2 K by using a photocalorimetric (PC) detecting system. At lower temperatures, the photoluminescence (PL) quantum yield is muc...

Three kinds of luminescent crystals, copper(I) cluster compounds with different ligand configurations (hexanuclear methylpyridinethiolato-copper(I): [Cu 6 (n L -mpyt) 6 ]; n L being the ligand configuration), have been investigated by observing th...

Luminescence spectra of doped and undoped GaAs/GaAlAs and InGaAs/GaAs/GaAlAs structures containing several tens of stepped quantum wells (QW) are investigated. The emission bands related to free and bound excitons and impurity states are observed ...

Dynamical processes of high-density excitons and their relaxation mechanisms in GaSe crystals have been investigated in real and momentum spaces by observing resonant luminescence spectra of the excitons in the time- and space-resolved regimes. Te...

Microcrystals of iodates of mercury, lead, thallium, and bismuth were grown in pores of glass and polymer matrices from solutions or through sublimation in vacuum. Images of these microcrystals embedded in matrices were obtained with an electron m...

Photoinduced high-density phase of exciton-polariton masses excited at a two-dimensional stacking fault interface in BiI 3 has been studied by observing the degenerate four-wave-mixing (DFWM) signals. It was found that the increase in the dephasin...

In Al x Ga 1-x As/AlAs quantum wire (QWR) structures, the lower lying indirect exciton (IE) photoluminescence (PL) peak shows remarkable blue-shift under intense light-excitation contrary to the higher lying direct exciton (DE) PL band with very s...

Spatial correlation of a quantum coherence of weakly interacting stacking fault excitons (SFEs) excited heavily at a two-dimensional stacking fault interface in BiI 3 has been studied by performing the degenerate four-wave-mixing (DFWM) measuremen...

Spatial evolution of heavily photo-created excitons in GaSe single crystals has been studied by observing space- and time-resolved photoluminescence. At an early stage, the free-exciton recombination band shows a blue-shift with broadening due to ...

Under intense light excitation, dynamical processes on indirect and direct excitons (DEs) at high density in Al x Ga 1-x As/AlAs quantum wire (QWR) structures have been investigated. The high density effects are characterized by the spectral blue-...

The relaxation dynamics of photo-excited states in single crystals of Alq 3 , utilized as organic electroluminescent (EL) devices, have been investigated. The photoluminescence (PL) peak of Alq 3 changes depending on the exciting photon energy and...

Spatial behavior of the stacking fault excitons (SFE's) excited heavily in a two-dimensional space at a stacking fault interface in Bil 3 has been studied. The SFE's whose center-of mass motion is confined at the interface show more efficient spa...

High density excitation effects on excitons in Al x Ga 1-x As/AlAs (x=0.2?0.5) quantum wires (QWRs) have been investigated. In these samples, the difference between the type-I (x?0.3) and type-II (x?0.4) band structures was clearly observed in hig...

Spatial and temporal behavior of excitons heavily excited in a quasi-two-dimensional space of a stacking fault interface in BiI 3 has been studied by space- and time-resolved luminescence measurements. The luminescence spectra show the peak-energy...

High-density effects on the exciton states in a layered GaSe single crystal have been studied by observing photo-luminescence and degenerate four-wave-mixing (DFWM) signals. The luminescence peak of the lowest exciton states shifts from lower ener...

Quantum confinement effects and nonlinear luminescence of excitons in CuI microcrystallites on the substrates of poly-methyl methacrylate have been studied. Exciton transitions due to the hexagonal structure appear in the disk-shaped microcrystall...

Spatial behavior of excitons at high density was studied in a specific exciton system at a quasi-two-dimensional planar defect in layered BiI 3 crystals. Space- and time-resolved resonance luminescence spectra of the exciton slate shows clear blue...

We study spatial behavior of heavily excited excitons localized at a two-dimensional space of a specific stacking fault interface in a layered crystal (Formula presented) Pump-and-probe absorption and resonant luminescence spectra of the exciton s...

We present transport properties of excitons at high density in a quasi-two-dimensional space of a specific stacking disorder interface in layered crystal BiI 3 , observing temporal behavior and peak energy shifts in space- and time-resolved lumine...

The optical response of excitons confined in characteristic nanostructures in layered metal tri-iodide crystals introduced by some irregular stackings from the bulk structures is reviewed. In BiI 3 a specific stacking fault takes place during crys...

Macroscopic and efficient spreading of excitons from an exciting laser spot to the outside area along a quasi two-dimensional space of a planar-defect in BiI 3 is presented by space- and time-resolved photoluminescence, and the degenerate Four-Wav...

The size effects on the exciton absorption and luminescence spectra are studied in nanostructure of BiI 3 embedded in the matrices of bulk BiI 3 and CdI 2 crystals. The quantum-confined exciton states are observed as the absorption lines of the se...

Macroscopic exciton transport phenomena from a small area of an exciting laser spot to outside the spot along a quasi-two-dimensional planar defect in BiI 3 , are presented from space-resolved pump-probe absorption, photoluminescence, and four-wav...

Microcrystallites and ultra-thin films of BiI 3 embedded in CdI 2 crystals were prepared by the melt-growth method and the hot wall technique. Absorption spectra and Stokes-shifted photoluminescence bands of the excitons confined in those are pres...

The magnetic field dependence of exciton photoluminescence intensity was investigated in GaAs/AlGaAs superlattice and quantum well structures for high magnetic fields up to 40 T. We discuss the observed large magnetic field effects in terms of the...

We report the optical nonlinear response of the confined excitons in nanostructures induced by external stress in a layered crystal BiI 3 . The absorption intensity of the confined excitons is saturated by intense laser excitation. We clarify the ...

Raman absorption of the exciton and luminescence from self-trapped exciton in SbI 3 and BiI 3 have been investigated under hyrostatic pressure. The difference in the nature of intra-layer bonding between these materials brings about the difference...

The high density effects of excitons excited at a two-dimensional stacking-fault plane in layered BiI 3 crystal is investigated. The blue-shift and broadening have been observed for the high density excitation. A new transition appears below the r...

Raman absorption of the exciton and luminescence from self-trapped exciton in SbI 3 and BiI 3 have been investigated under hyrostatic pressure. The difference in the nature of intra-layer bonding between these materials brings about the difference...

Saturation spectra of the excitons confined and localized at several kinds of stacking disorders in layered crystal BiI 3 are studied. The quasi-two dimensional exciton localized at the stacking fault interface does not saturate its absorption str...

The exciton spectra of Sn02 single crystals with the low and high concentrations of the oxygen vacancies (OV) are investigated. The series of luminescence lines adjacent to the lowest free exciton states (the excitons localized by the isolated OV ...

Absorption line series W J (J=I,II,III,…) appeared below the indirect edge in BiI 3 has been studied. The series is assigned to the excitons confined in mesoscopic domains produced by deformation faults characteristic of layered materials. Each li...

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 Bil 3 crystals. The ultrafast response of the blue-shift due to the optical Stark effect(OSE) is c...

On the exciton states localized at a two-dimensional stacking fault interface in a layered crystal BiI 3 , some nonlinear optical phenomena clearly appear reflecting large transition probability. The optical Stark shift and other high density exci...

Fast and ballistic spreading of excitons excited at the stacking fault interface in BiI 3 crystals was observed in the temporal behavior of exciton luminescence with space- and time-resolved measurements. The spreading velocity reaches ?7 × 10 8 c...

We present the observation of an optical Stark effect on multiple exciton states localized at a stacking fault in layered crystal BiI3. The level anticrossings concerning the crystal ground state as well as the multiple exciton states are clearly ...

Summary form only given. The time-resolved optical Stark effect (OSE) with high spectral resolution is presented for a characteristic exciton system. In the layered crystal BiI 3 , several sharp absorption lines appear near the absorption edge. Th...

The luminescence decay processes of the three ground-state excitons localized at a stacking fault with quasi two-dimensional symmetry in layered BiI 3 crystals were investigated in the picosecond time domain. The characteristic time behaviour of t...

The study of exciton transfer along the stacking fault interface in BiI 3 crystals is presented by using a newly designed space-resolved spectroscopy method. The resonant luminescence lines of the excitons with exact zero Stokes shift were observ...

We have studied photocalorimetric spectra (PCS) of characteristic exciton transitions in Bil 3 crystals. Our PCS measuring system has the sensitivity of less than 10 -12 J - for the detection of photo-thermal heating after photo-excitation. The...

The direct observation of propagation of the excitons confined at the stacking fault interface in layered BiI 3 is presented by using a newly designed space-resolved spectroscopy. Extraordinary large diffusion constants of more than 10 5 cm 2 /sec...

The optical Stark effect of an exciton system localized at a stacking fault (stacking fault excitons, SFE) in BiI 3 crystals is presented. The SFE states show three very sharp absorption lines called R, S, and T. The excitation laser frequency de...