Search

Infrared (IR) absorption and Raman spectra of methane hydrate (MH) were measured at low temperatures and high pressures to reveal the dynamics and cage occupancy of CH4 molecules and the hydration ...

A helical metallofoldamer forms a columnar phase with high thermal stability owing to its rigid helical mesogenic structure.

We demonstrate the formation of grid-type (crossed perpendicular to each other) fibrous assemblies of low-molecular-weight gelators in aligned liquid-crystalline smectic templates. In the template of layered structures, a gelator forms oriented fibers with one directional and two orthogonal directional (grid-like) alignment depending on the order of layered structures.

Accumulated charge measurement (ACM) is a new experimental technique for organic semiconductors to evaluate the charge injection barrier at the semiconductor–metal interface directly using a metal–insulator–semiconductor–metal (MISM) capacitor. In this technique, the precise estimation of the electrostatic capacity of the insulator layer (CI) is required for the analysis. The information of this parameter is, in principle, included in the ACM data; however, it is not directly evaluated because of the error resulting from the charge-spreading effect in an organic MISM capacitor with an unrestricted electrode structure. Therefore, the CI in previous ACM experiments has been independently estimated from the area of the electrode. In this study, a novel design of a substrate with a restricted-bottom-electrode structure is reported. Using the newly designed substrate, it was possible to suppress the charge-spreading effect and successfully estimate precise values of CI directly from the ACM data. Subsequently, it was possible to evaluate the injection barriers at the metal-free phthalocyanine (H2Pc)–Ag and pentacene–Au interfaces, which were 0.4 and 0.15 eV, respectively. The built-in potentials in the semiconductor layer were also determined for the samples used in the measurement.

The electronic structures of platinum-group metal pernitrides MN2 (M = Ru, Rh, Ir, and Pt) were investigated via synchrotron radiation infrared spectroscopy and first-principles calculations. Measured reflectance spectra of marcasite-type RuN2 and RhN2 showed Drude-like responses, approaching 1 as the photon energy was decreased, whereas reflectance of arsenopyrite-type IrN2 and pyrite-type PtN2 became ∼0.3 in the low photon energy region with a few features. These findings agreed well with the predictions of the metallic nature of marcasite-type RuN2 and RhN2 and the semiconducting properties of arsenopyrite-type IrN2 and pyrite-type PtN2, respectively. The measured reflectance spectra were also reasonably consistent with the calculated optical responses. The band gaps of IrN2 and PtN2 were estimated to be 0.8 and 2.1 eV, respectively, via first-principles calculation with a modified Becke–Johnson (MBJ) potential for the exchange potential., ファイル公開：2021-04-01

Infrared synchrotron radiation (IR-SR) is a broad-band light source. Its brilliance is the main advantage for microspectroscopy experiments, when the limited size of the sample often prevents the use of conventional thermal radiation sources. Cultural heritage materials are delicate and valuable, therefore, nondestructive experiments are usually preferred. Nevertheless, sometimes, small pieces can be acquired in the process of preservation and conservation. These samples are analyzed by various experimental techniques and give information about the original material and current condition. In this paper, four attempts to analyze cultural heritage materials are introduced. All these experiments are performed at the microspectroscopy station of IR beamline BL43IR in SPring-8.

Recently, the high-brilliance infrared synchrotron radiation source out of various infrared sources has become popular, and it is widely used in many fields of studies. For spectroscopy, the HgCdTe (MCT) detector is often used. It covers a wide mid-infrared region and has high sensitivity, but saturates easily. In this work, the detector saturation behavior was investigated in detail using infrared synchrotron radiation and infrared free electron laser. We found that the saturation and its elimination show various patterns depending on the amplifier gain, light intensity and the time structure of the light. The influence of the saturation to the spectral shape is also discussed.

Our previous study remained a question why biogenic guanine crystals that cause magnetic orientation under magnetic fields scattered light so intensively. In addition, the magnetic orientation analyses indicated that the crystal plate has primal and second axes of easy magnetization by diamagnetism, by which two-stage orientation of the crystal is caused. This paper aims to reveal the molecule arrangement inside the guanine crystal, which is related to optical and magnetic anisotropy. A transient light scattering increase from the guanine crystals that occurs with increasing and decreasing magnetic fields between 0 and 0.5 T was measured. The results indicate that the biogenic guanine crystal plates have a specific direction to scatter the light incidence. In the next, molecular vibrations in a single-crystal plate were investigated by utilizing the synchrotron microscopic Fourier transform infrared (FTIR) spectroscopy, and the obtained spectrum compared with that in magnetically oriented guanine crystal. The FTIR and attenuated total reflectance measurements reproducibly observed the IR absorbance spectrum peak appearance and disappearance when the polarization direction was set parallel and perpendicular to the morphological length of a biogenic guanine crystal. It is speculated that spectrum peak appearance and disappearance were caused by vibration of C = O bonds and N-H bonds in guanine crystal for polarization direction. In conclusion, we revealed that the surface and inside of biogenic guanine crystal possessed the anisotropy for molecule orientation related to optical and magnetic property.

We report the status of a scattering near-field microspectroscopy apparatus developed at SPring-8 using an infrared synchrotron radiation (IR-SR) source. It consists of a scattering type scanning near-field optical microscope and a Fourier transform infrared spectrometer. The IR-SR is used as a highly brilliant and broad-band IR source. This apparatus has potential for application in near-field spectroscopy with high spatial resolution beyond the diffraction limit. In order to eliminate background scatterings from the probe shaft and/or sample surface, we used higher harmonic demodulation method. The near-field spectra were observed by 2nd harmonic components using the lock-in detection. The spatial resolution of about 300 nm was achieved at around 1000 cm− 1 (10 μm wavelength).

We report a first-time attempt of diffusion control of impurities by IR excitation, by using an intensive synchrotron radiation facility, BL43IR of SPring-8. Although the result is discouraging, the plan, experimental setup, irradiation experiment, and the result on the impurity diffusion, are described in detail, in hoping improvement of experiment in the future. It is suggested that the input power employed in the present experiment is not enough to observe the intended results.

BL43IR at SPring-8 is overviewed regarding the beamline properties on the flux, the brilliance and the noise in comparison with the conventional thermal radiation (TR). The flux is comparable to the TR, and what makes the most of BL43IR is to utilize the high brilliance. We redirect our strategy to concentrate on the microscopes with highly brilliant infrared radiation from SPring-8 and attract the vast TR spectroscopy community.

Vibration bands of dielectric ceramics appear at a mid-infrared (MIR) and those position and shape are changed owing to change environment of crystal lattice. Therefore, micro-focus MIR spectroscopy is a one of useful tool to evaluate very small size capacitor (e.g. smaller than 0.5 mm in chip size). Very small size multi-layer capacitor: MLCC are one of very important device to produce high quality electrical products such as cell phone, etc. Quality and reliability of MLCC are corresponding to not only average dielectric properties but also local fluctuation of them. Furthermore, local fluctuation of dielectric properties of MLCC could evaluate with MIR spectroscopy. It is possible to obtain a satisfied MIR spectrum from small size samples performed by a micro-focus spectrometer combined with synchrotron radiation as a high luminance light source at beam line BL43IR of SPring-8. From the above result, it is possible to evaluate the degree of homogeneity by comparing the shape change of Ti–O peak on IR spectra.

Troglitazone exists as four isomers in equal amount and these isomers compose two racemic compounds, RR/SS and RS/SR. The objective of this study was to discriminate between the racemic compounds and between the crystal and amorphous forms of troglitazone in solid dispersions (SDs) using IR-to-THz imaging. SDs of troglitazone with polyvinylpyrrolidone (PVP, carrier) were prepared by the closed melting method. SDs were heated at various temperatures and water content. The mid-to-far infrared measurements for the powder samples were performed by using the synchrotron radiation source at the BL43IR in SPring-8. Crystalline RR/SS (L) and RS/SR (H) showed different spectra, that is, each form had a specific peak, respectively. However, amorphous forms prepared from each crystalline form exhibited the same spectra. Using the chemo-metric analysis, the existing component was decided in each pixel and the distribution of crystalline L, H and amorphous troglitazone in SDs could be illustrated. For the sample heated at 105 °C, 75%RH, scattered plots of H and amorphous against PVP showed the trend for H was negative; on the other hand, amorphous showed positive correlation. This result suggested that H existed separately, whereas amorphous would be dissolved in PVP. Based on these evaluations, it was clear that the physical state and distribution of troglitazone in SDs, including the discrimination between L, H, and amorphous, reflect the preparation conditions. Chemical imaging can observe a difference in the dispersed state of drug and ingredient in a visible image by performing statistical processing.

To elucidate the pressure evolution of the electronic structure in an antiferromagnetic dimer-Mott (DM) insulator ${\ensuremath{\beta}}^{\ensuremath{'}}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}{\mathrm{ICl}}_{2}$, which exhibits superconductivity at 14.2 K under 8 GPa, we measured the polarized infrared (IR) optical spectra under high pressure. At ambient pressure, two characteristic bands due to intra- and interdimer charge transfers have been observed in the IR spectra, supporting that this salt is a typical half-filled DM insulator at ambient pressure. With increasing pressure, however, the intradimer charge transfer excitation shifts to much lower energies, indicating that the effective electronic state changes from half-filled to 3/4-filled as a result of weakening of dimerization. This implies that the system approaches a charge-ordered state under high pressure, in which charge degrees of freedom emerge as an important factor. The present results suggest that charge fluctuation inside of dimers plays an important role in the high-temperature superconductivity.

Mordenite (structure type MOR) is one of nano-porous crystals of aluminosilicate zeolites. The framework of mordenite has one-dimensional channels along the c-axis. Cations, such as Na, are distributed at the side pockets of channels. We measured polarized far infrared absorption spectra of Na-type mordenite single crystals with the size of less than ∼100 μm. The measurements were performed by the microspectroscopy station of BL43IR at SPring-8. The polarization directions are set for parallel and perpendicular to the c-axis. The polarization dependence is observed clearly in the spectra. Absorption peaks are observed at 140 and 320 cm−1 for parallel polarization and at 170 and 280 cm−1 for perpendicular polarization. They are assigned to the anisotropic motion of Na cations and framework. The spectra are compared with the ordinary absorption spectra of the pellet forms of Na-, Rb- and H-type mordenite powders.

Potassium clusters are stabilized in the cages of low silica X zeolite, where the cages with the inside diameter of ∼13 A are arrayed in a diamond structure. The average number of potassium atoms per cage, n, is changed from ∼6.3 to the saturated value of ∼8.8 by controlling the guest potassium loading density. The temperature dependence of magnetization shows the typical behavior of the N-type ferrimagnetism at n∼6.8 and n∼8.3. The zero field μSR spectra show significant increase in the relaxation rate below the Curie temperature, 5 K, in the sample with n∼6.8. The time dependence of asymmetry shows almost full amplitude of decrease, indicating that the internal field below the magnetic phase transition arises in the almost full volume of the sample. The longitudinal field μSR spectra at 1.7 K show the typical decoupling behavior of a static internal field. A model of ferrimagnetism is proposed based on the structure of the zeolite, where a magnetic sublattice of itinerant electron ferromagnetism is assumed.

BL43IR of SPring-8 has been constructed for the infrared materials researches, and it covers a wide spectral range from 100 to 20,000 cm −1 . The microspectroscopy station of this BL has a spatial resolution smaller than 10 μm in diameter in the mid-infrared region without apertures. This station had been mainly used within mid-infrared region, and its performance in the far-infrared region had not been tested. In this paper, we examined the capability of the microscope in the far-infrared region and the spatial resolution is found to be almost at the diffraction limit. The microspectroscopy station has been revealed to have a good performance for doing materials researches in all the spectral range available.

Lithiated polysilane was synthesized by the mechanochemical reaction of layered polysilane with metallic lithium. The resulting dark green powder formed a Si–Li bond on the surface and demonstrated electroconductivity.

Mutually interacting potassium clusters stabilized in supercages of aluminosilicate zeolite FAU (Si/Al=1), the so-called low-silica X, are investigated in terms of optical and magnetic properties. FAU is ion-exchanged to K, and denoted by K-FAU(1), hereafter. When metal K is adsorbed at the average loading density of 0.7±0.3 atom per supercage of FAU, the observed infrared absorption is more than one order weaker than that in similarly K-loaded samples of K-FAU(1.25) which is called X commonly. The Weiss temperature in K-loaded K-FAU(1) is −33±3 K. This value is several times larger than that in K-loaded K-FAU(1.25). The Mott insulator phase in K clusters in FAU(1), is thought to be realized differently from the metallic phase of K-FAU(1.25).

The authors report infrared near-field spectroscopy using synchrotron radiation at BL43IR, SPring-8 in the finger print region. At the microspectroscopy station, the infrared synchrotron radiation beam is focused on a cantilever probe with a 3 μm square aperture. A comb-shaped Au electrode with the width of 3 μm and the distance of 3 μm is used for the reflection measurement. The Au electrodes can be resolved at 650 cm−1 and the resolution is estimated to be λ/5.

We find a characteristic low-energy peak structure located in the range 100--300 cm${}^{\ensuremath{-}1}$ in the optical conductivity spectra of a quasi-two-dimensional organic compound with a triangular lattice, $\ensuremath{\theta}$-${(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}{\mathrm{CsZn}(\mathrm{SCN})}_{4}$, in which two different types of short-range charge orderings (COs) coexist. Upon lowering the temperature, the low-energy peak becomes significant and shifts to much lower frequencies only for the polarization of $\mathbit{E}\ensuremath{\parallel}\mathbit{a}$, in contrast to the other broad electronic bands in the midinfrared region. On introducing disorder, the low-energy peak is strongly suppressed in comparison with the broad electronic bands. This result indicates that the low-energy peak is attributed to a collective excitation that originates from the short-range CO with a relatively long-period $3\ifmmode\times\else\texttimes\fi{}3$ pattern. The present results shed light on the understanding of the low-energy excitation in the glassy electronic state, where the charge degrees of freedom remain at low temperatures.

The magnetization process of potassium clusters arrayed in zeolite LTA is measured up to 14 T. This material shows ferromagnetism at certain concentrations of potassium atoms in cluster. The magnetization at ferromagnetic concentrations increases linearly with the applied magnetic field at higher fields. This result is well explained by a spin-cant model of antiferromagnet. A largeness of an estimated spin-cant angle is assigned to the Dzyaloshinsky-Moriya interaction strongly enhanced by the degeneracy of 1p-orbital of cluster.

μSR has been studied for a ferromagnetic sample of K clusters in zeolite LTA as a function of longitudinal field (LF) and temperature. Under weak LF a non-relaxing asymmetry component is produced at low temperatures, whereas at higher temperatures in the paramagnetic state a two-component relaxation is clearly observed. The data are successfully explained by assuming two different muon-stopping sites in the cubic antiferromagnet, along with a canting of the spin structure.

Optical conductivity [{delta}({omega})] of PrRu{sub 4}P{sub 12} has been studied under high pressure to 14 GPa, at low temperatures to 8 K, and at photon energies 12 meV-1.1 eV. The energy gap in {delta}({omega}) at ambient pressure, caused by a metal-insulator transition due to an unconventional charge-density-wave formation at 63 K, is gradually filled in with increasing pressure to 10 GPa. At 14 GPa and below 30 K, {delta}({omega}) exhibits a pronounced Drude-type component due to free carriers. This indicates that the initial insulating ground state at zero pressure has been turned into a metallic one at 14 GPa. This is consistent with a previous resistivity study under pressure, where the resistivity rapidly decreased with cooling below 30 K at 14 GPa. The evolution of electronic structure with pressure is discussed in terms of the hybridization between the 4f and conduction electrons.

Magnetic and optical properties of Rb clusters in aluminosilicate zeolite LTA are investigated in detail. These clusters are stabilized in supercages arrayed in a simple cubic structure. The average number of s-electrons confined in each cluster, n , is changed up to the nearly saturated value ∼4.6. At n >2, the absolute value of the negative Weiss temperature increases with increasing n . In saturated samples at n ∼4.6, ferromagnetic properties are observed below the asymptotic Curie temperature 3 K, but the fraction of the spontaneous magnetization is found to be very small and incomplete. Magnetic properties are different from those of K clusters in LTA, and discussed in relation to residual K cations.

Magnetic properties are investigated for potassium clusters arrayed in zeolite LTA. The potassium loading density per cluster, n, is changed up to 7.2 per cluster. The n-dependence of the Curie constant and the magnetization are measured in detail. Possible origins of ferromagnetic properties are discussed. ( 2000 Elsevier Science B.V. All rights reserved.

K and Na clusters are generated in zeolite FAU with an Si-to-Al ratio of 1.25. We measured magnetic susceptibility, electron}spin resonance spectrum and the optical one. Observed magnetic properties are discussed from the viewpoint of the correlated electrons and/or the narrow energy band with a properly localized nature of clusters, together with a "nite disorder e!ect. ( 2000 Elsevier Science B.V. All rights reserved.

Far-infrared spectroscopy has been performed on [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic) single crystals, to probe changes in the molecular vibrations upon the photoinduced and temperature-induced spin crossovers. Synchrotron radiation has been used as the farinfrared source to overcome the strong absorption and the small sizes of the samples. Absorption lines due to FeN6 cluster vibrations, observed below 400 cm-1, show strong intensity variations upon the crossover due to the deformation of FeN6 between high-spin and low-spin states. However, they remain almost unchanged between the photo- and temperature-induced high-spin states. This is in sharp contrast to the lines at 500-700 cm-1 due to intramolecular vibrations of the picolylamine ligands, which show marked variations between the two high-spin states. It is concluded that the most important microscopic difference between the two high-spin states arises from the ligands, which is likely to reflect different states of intermolecular bonding between them., Comment: 10 pages, 4 figures