Effects of indium doping on the superconducting properties of YBa2Cu3Oy sintered compounds and thin films

We investigated the effects of indium doping on the superconducting properties of YBCO sintered samples and thin films. In₂O₃-doped YBCO and YBa₂Cu_3−xIn_xO_y sintered samples showed a gradual decrease in the critical temperature (T_c) with increasing indium content; however, a T_c value above 80 K was maintained even up to 30 vol.% addition and x = 0.4, respectively. Ba₃Cu₃In₄O₁₂ was detected by X-ray diffractometry and energy-dispersive X-ray spectroscopy as a reaction product for both sintered samples. The normalized J_c under a magnetic field of 0.1 T showed a maximum at x = 0.3. Indium-doped YBCO films prepared by pulsed laser deposition showed a similar dependence of T_c on indium content as the sintered samples.     

Adsorbate-localized versus substrate-mediated excitation mechanisms for generation of coherent Cs-Cu stretching vibration at Cu(111)

Coherent Cs-Cu stretching vibration at a Cu(111) surface covered with a full monolayer of Cs is observed by using time-resolved second harmonic generation spectroscopy, and its generation mechanisms and dynamics are simulated theoretically. While the irradiation with ultrafast pulses at both 400 and 800 nm generate the coherent Cs-Cu stretching vibration at a frequency of 1.8 THz (60 cm(-1)), they lead to two distinctively different features: the initial phase and the pump fluence dependence of the initial amplitude of coherent oscillation. At 400 nm excitation, the coherent oscillation is nearly cosine-like with respect to the pump pulse and the initial amplitude increases linearly with pump fluence. In contrast, at 800 nm excitation, the coherent oscillation is sine-like and the amplitude is saturated at high fluence. These features are successfully simulated by assuming that the coherent vibration is generated by two different electronic transitions: substrate d-band excitation at 400 nm and the quasi-resonant excitation between adsorbate-localized bands at 800 nm, i.e., possibly from an alkali-induced quantum well state to an unoccupied state originating in Cs 5d bands or the third image potential state.     

神经网络与紫外光谱法同时测定芳香类化合物

测定了苯酚、苯胺、α萘胺、间二硝基苯及对氧基苯甲醛混合体系的紫外光谱，用神经网络法直接对混合体系紫外光谱数据进行处理，成功地测定了混合体系各组分含量，结果良好     

Validation of intermolecular pair potential model of SiH4: molecular-dynamics simulation for saturated liquid density and thermal transport properties

We demonstrate a validation of the intermolecular pair potential model of SiH(4), which is constructed from ab initio molecular-orbital calculations and expressed as the sum of the exponential and the London dispersion terms. The saturated liquid densities of SiH(4) are calculated for temperatures from 100 to 225 K by molecular-dynamics (MD) simulation. The average deviation between the experiment and the MD simulation using the present potential model is 3.9%, while the deviations exceed 10% for other well-known potential models such as the five-center Lennard-Jones (LJ) model. Subsequently, the shear viscosity, the thermal conductivity, and the self-diffusion coefficient of liquid SiH(4) are calculated by an equilibrium MD simulation with the Green-Kubo formula from 100 to 225 K. The average deviations from experiment are 11.8% and 13.7% for the shear viscosity and the thermal conductivity, respectively. Comparing the present model with an empirical one-center LJ model, it turns out that the rotational energy transfer through the intermolecular potential energy, which comes from the anisotropic potential energy, plays an important role in the thermal conductivity of liquid SiH(4). These results indicate that the present intermolecular potential model has an ability to give realistic pictures for liquid SiH(4) through molecular simulations.     

Identification of oxidation states of metal oxides by MALDI-TOF MS

For the detection of inorganic species, we have developed chemical reaction laser desorption ionization mass spectrometry, and applied it to the analysis of metal oxides in different oxidation states. Metal oxide species insoluble in common organic solvents were finely grounded in a mortar and suspended in a solvent. The turbid suspension was placed on a sample holder on which a suitable chelating reagent had been previously spotted in a similar manner for sample preparation employed in the matrix-assisted laser desorption mass spectrometry (MALDI-MS). By using this method, the mass spectra of manganese (II and IV) oxides (MnO and MnO₂), cobalt (II and III) oxides (CoO and Co₂O₃), and chromium (III and VI) oxides (Cr₂O₃ and CrO₃) were successfully obtained. By adjusting the experimental conditions, such as ionization modes and chelating reagents, the non-identical mass spectra were obtained for the elements in the different oxidation state. Thus, the oxidation states could be identified clearly.     

Design of ionic liquids as a medium for the Grignard reaction

Design of novel phosphonium ionic liquids that are compatible with Grignard reagents have been investigated; several types of phosphonium salts that have an alkyl ether moiety have been synthesized and their capability evaluated as solvents for Grignard reagents. It has been established that even basic aliphatic Grignard reagent-mediated reactions are possible when methoxyethyl(tri-n-butyl)phosphonium bis(trifluoromethanesulfonyl)imide is used as the solvent.     

Two-dimensional iron(II) spin crossover complex constructed of bifurcated NH...O- hydrogen bonds and pi-pi interactions: [FeII(HLH,Me)2](ClO4)2.1.5MeCN (HLH,Me = imidazol-4-yl-methylidene-8-amino-2-methylquinoline)

A 2D iron(II) spin crossover complex, [FeII(HLH,Me)2](ClO4)2.1.5MeCN (1), was synthesized, where HLH,Me = imidazol-4-yl-methylidene-8-amino-2-methylquinoline. 1 showed a gradual spin transition between the HS (S = 2) and LS (S = 0) states from 180 to 325 K within the first warming run from 5 to 350 K, in which 1.5MeCN is removed, and there was an abrupt spin transition at T1/2 downward arrow = 174 K in the first cooling run from 350 to 5 K. Following the first cycle, the compound showed an abrupt spin transition at T1/2 upward arrow = 185 K and T1/2 downward arrow = 174 K with 11 K wide hysteresis in the second cycle. The crystal structures of 1 were determined at 296 (an intermediate between the HS and LS states) and 150 K (LS state). The structure consists of a 2D extended structure constructed of both the bifurcated NH...O- hydrogen bonds between two ClO4- ions and two neighboring imidazole NH groups of the [FeII(HLH,Me)2]2+ cations and the pi-pi interactions between the two quinolyl rings of the two adjacent cations. Thermogravimetric analysis showed that solvent molecules are gradually eliminated even at room temperature and completely removed at 369 K. Desolvated complex 1' showed an abrupt spin transition at T1/2 upward arrow = 180 K and T1/2 downward arrow = 174 K with 6 K wide hysteresis.     

Synthesis of multisubstituted furans, pyrroles, and thiophenes via ynolates

An efficient synthetic method for the preparation of multisubstituted furans, thiophenes, and pyrroles using ynolates was developed. This novel formal [4 + 1] annulation by C2-C3 and C3-C4 bond formations includes cycloaddition, cyclization, decarboxylation, and dehydration as key steps.