Addition to electron deficient olefins of alpha-oxy carbon- centered radicals, generated from cyclic ethers and acetals by the reaction with alkylperoxy- lambda(3)-iodane

Thermal decomposition of 1-tert-butylperoxy-1,2-benziodoxol-3(1H)-one in cyclic ethers and acetals at 50 degrees C generates alpha-oxy carbon-centered radicals, which undergo an addition reaction with vinyl sulfones and unsaturated esters.     

Syntheses of a series of octaethylporphyrin-benzoquinone linked molecules as a model for the primary process of photosynthesis

To clarify the primary process of photosynthesis, a series of model compounds, in which an octaethylporphyrin and a benzoquinone ring are connected with different lengths of a polymethylene chain, were synthesized and their photophysical properties were investigated.     

Einstein-de Haas effect in dipolar Bose-Einstein condensates

The general properties of the order parameter for a dipolar spinor Bose-Einstein condensate are discussed based on symmetries of interactions. An initially spin-polarized dipolar condensate is shown to dynamically generate a nonsingular vortex via spin-orbit interactions--a phenomenon reminiscent of the Einstein-de Haas effect in ferromagnets.     

Development of ultra-short pulse VUV laser system for nanoscale processing

We have developed intense vacuum ultraviolet (VUV) radiation sources for advanced material processing, such as photochemical surface reactions and precise processing on a nanometer scale. We have constructed a new VUV laser system to generate sub-picosecond pulses at the wavelength of 126 nm. A seed VUV pulse was generated in Xe as the 7th harmonic of a 882-nm Ti:sapphire laser. The optimum conversion was achieved at the pressure of 1.2 Torr. The seed pulse will be amplified by the Ar₂^*\mathrm{Ar}_{2}^{*} media generated by an optical-field-induced ionization Ar plasma produced by the Ti:sapphire laser. We have obtained a gain coefficient of g=0.16 cm⁻¹. Our developing system will provide VUV ultra-short pulses with sub-μJ energy at a repetition rate of 1 kHz.     

Generation of subpicosecond vacuum ultraviolet pulses at 126 nm by using harmonics of a subpicosecond Ti:Sapphire laser

Subpicosecond vacuum ultraviolet (VUV) pulses at the wavelength of 126 nm have been generated in rare gases as a result of the 7th harmonic radiation of a subpicosecond Ti:Sapphire laser oscillating at 882 nm. The VUV harmonic intensity was optimized in Xe at the pressure of 1.2 Torr. The behavior of the harmonic emission was qualitatively reproduced by the classical nonlinear optics. The increase of the harmonic intensity was limited by multiphoton ionization of Xe.     

Quasi-Nambu-Goldstone modes in Bose-Einstein condensates

We show that quasi-Nambu-Goldstone (NG) modes, which play prominent roles in high energy physics but have been elusive experimentally, can be realized with atomic Bose-Einstein condensates. The quasi-NG modes emerge when the symmetry of a ground state is larger than that of the Hamiltonian. When they appear, the conventional vacuum manifold should be enlarged. Consequently, topological defects that are stable within the conventional vacuum manifold become unstable and decay by emitting the quasi-NG modes. Contrary to conventional wisdom, however, we show that the topological defects are stabilized by quantum fluctuations that make the quasi-NG modes massive, thereby suppressing their emission.     

Synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure study on oxidative etching of diamond-like carbon films by hyperthermal atomic oxygen

Surface structural changes of a hydrogenated diamond-like carbon (DLC) film exposed to a hyperthermal atomic oxygen beam were investigated by Rutherford backscattering spectroscopy (RBS), synchrotron radiation photoelectron spectroscopy (SR-PES), and near-edge X-ray absorption fine structure (NEXAFS). It was confirmed that the DLC surface was oxidized and etched by high-energy collisions of atomic oxygen. RBS and real-time mass-loss data showed a linear relationship between etching and atomic oxygen fluence. SR-PES data suggested that the oxide layer was restricted to the topmost surface of the DLC film. NEXAFS data were interpreted to mean that the sp² structure at the DLC surface was selectively etched by collisions with hyperthermal atomic oxygen, and an sp³-rich region remained at the topmost DLC surface. The formation of an sp³-rich layer at the DLC surface led to surface roughening and a reduced erosion yield relative to the pristine DLC surface.     

Molecular Statistical Theory of the Frank Elastic Constants of Liquid Crystals

Abstract

The Frank elastic constants K ₁, K ₂, K ₃ are calculated in the mean field approximation by assuming that the intermolecular force is the sum of hard rod repulsion (length L and width D) and Maier-Saupe's type attraction. The main conclusions are as follows. (1) the inequlaities K ₃? K ₁ > K ₂ necessarily hold. (2) All the K'_is are nearly proportional to the square of the orientational order parameter S. (3) In thermotropic system, K ₁/S ², K ₁/K and K ₂/K(K: mean elastic constant) increase slowly and K _3/K, K ₃/K ₁ decreases with L/D, whereas K/kT _c is nearly constant for L/D = 3 ～ 5. These tendecies agree fairly well with the observations on liquid crystals with almost rigid structure. (4) In the lyotorpic system in which L/D ? 1, K ₁/3 = K ₂ = cLk _T/3π D ² and k ₁/K ₃ = 4D/5cL are obtained (c: packing fraction). The estimate for PBLG solution nearly agrees with recent experimental data.     

Ethynylpyrene Linked Benzocrown Ethers as Fluorescent Sensors for Metal Ions

Substances containing ethynylpyrenes linked to either one or four benzocrown ethers were synthesized, and their absorption and fluorescence spectroscopic responses to metal ions were assessed. Addition of metal perchlorates to solutions of these substances promotes short wavelength shifts in their absorption and fluorescence maxima and increases in their fluorescence intensities. The magnitudes of the fluorescence intensity increases are dependent on the ring size and number of the crown ether and the nature of the metal cation. Association constants for complex formation were calculated using fluorescence intensity versus concentration data. Analysis using Job's plots showed that the substances containing one benzocrown ether moiety form 1:1 complexes with metal ions. Results of experiments employing repeated addition and removal of Mg(ClO₄)₂ demonstrate that the ON‐OFF fluorescence response can be repeated at least three times. Results of molecular orbital calculations show that complexation with metal ions lowers the energies of both the π and π* levels of the ethynylpyrene moiety and that in some cases the vacant orbital on the metal becomes the LUMO of the complex. An explanation of the spectroscopic changes promoted by metal ions is proposed in terms of electrostatic repulsion and structural regulation.     

Determination of structures of cobalt(II)-chloro complexes in hydrochloric acid solutions by X-ray absorption spectroscopy at 298 K

The anion exchange reaction is fundamental to the adsorption and desorption of a specific species from a solution phase to an extracting phase, and it is widely used for separation and waste fluid treatment in industrial fields. However, the details of the anion exchange reaction are poorly understood. Quantitative thermodynamic analysis needs a precise solution condition before and after the exchange reaction. Identification of species adsorbed on the anion exchanger is also necessary because there are multiple species in the solution phase in general. Cobalt is a base metal that is widely used in modern society. One of the authors determined the distribution of cobalt-chloro complexes in hydrochloric acid solutions. It is necessary to know what species are adsorbed on anion exchangers for the thermodynamic analysis of the anion exchange reaction. The comparison in structures between the species in the solution phase and adsorbed on anion exchangers reveals what species are adsorbed. Therefore, the determination of the structures of cobalt-chloro complexes in the solution phase is the next step for quantitative analysis. X-ray absorption spectroscopy (XAS) was used for the structure analysis. Factor analysis can decompose extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) spectra consisting of multiple species into individual spectra of single species using the distribution determined using UV-Vis absorption spectra. Fitting EXAFS theoretical models to the decomposed individual spectra determined the structures of three cobalt-chloro complexes: an octahedron of [Co^II(H₂O)₆]²⁺, a distorted octahedron of [Co^II(H₂O)₅Cl]⁺, and a tetrahedron of [Co^IICl₄]^2?. The XANES spectra showed us that the Cl ligand in [Co^II(H₂O)₅Cl]⁺ was attracted to the center atom of Co^II by an electrostatic force, and the bonding system between Cl ligands and Co^II in [Co^IICl₄]^2? involved covalency.