Effect of interference pattern on femtosecond laser-induced ripple structure

Combined structures composed of a micron-sized periodic structure and a nano-sized quasi-periodic ripple structure were generated by a single process of multiple shots of an interfering femtosecond laser. The former structure was generated by an interference pattern and controlled by a number of beams. The latter structure was generated by a multiple shot method. As a result, multiple periodic structures were generated. The periodicity of the structures was analyzed by two-dimensional (2D) fast Fourier transform (FFT). The most probable period of ripple structure was downsized to 177 nm by restricting irradiated region by a TM wave interference pattern. The smallest period was 105 nm. The dispersion angle of a ripple decreased to about 50%. The period and direction of the ripples were for a first time controlled by using interference.     

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.     

Charge Transfer Transitions from Cyclohexadienyl-Type Radicals to Host Molecules in Anthracene Single Crystals

The optical absorption spectra of 1-, 2- and 9-dibenzo-cyclohexadienyl radical in anthracene crystals have been obtained and analyzed. It is shown that the absorption lines consist of vibrational progression and charge-transfer lines for 2- and 9-DBCR. Each line belonging to the former has the same polarization as the most intense 0–0 vibrational line and the latter show polarization character depending on the direction of charge transfer and the transition energy was found to have a coulombic dependence on the distance of charge transfer. It is pointed out that only charge transfer lines were observed for 1-DBCR. The splitting of lines were observed and ascribed either to the resonance transfer interaction between two neighboring molecules situated at an equal distance from the radical or to the site symmetry. It is suggested that the intensity of the charge-transfer lines are borrowed from the intra-radical transition. The result that the charge transfer lines are more intense than the intra-radical lines for 1-DBCR was discussed.     

Manganese centers with various valency in alkali halides

Abstract

Optical absorption bands and epr spectra of NaCl: Mn⁺⁺ X-irradiated at liquid nitrogen and room temperature are studied. Manganese epr spectra are divided into three classes, based on the value of hyperfme splitting constants. It is shown that the epr spectra with the hyperhe splitting constants of around 250 × 10-⁴, 80 × 10^?4 and 20 × 10^?4 cm^?1 are caused by Mn⁺, Mn⁺⁺ and Mn⁹, respectively. Formation of several manganese centers by X-irradiation is discussed. It is suggested that optical absorption bands at 410 and 440 nm are caused by Mn^O at the lattice site and that the Mn^O center which gives an epr spectrum with A = 15. 5 × 10^?4 cm^?1 is associated with a Mn⁰ center which is not at a substitutional site.     

Empirical determination of the random fraction in disordered channel

A new method of deriving the random fraction in a disordered channel : rom dechanneling experiments is described. In this method backscattering spectra obtained at two different doses are employed, with an assumption on the dose dependence of the defect concentration. The method is applied to the experimental data for B-implanted Si and it is found that the obtained random fraction is similar to the result of the diffusion calculation made by the present authors. The depth profiles of defects are also obtained and compared with the result of theoretical calculations.     

Soot formation characteristics in a lab-scale turbulent pulverized coal flame with simultaneous planar measurements of laser induced incandescence of soot and Mie scattering of pulverized coal

Soot formation characteristics of a lab-scale pulverized coal flame were investigated by performing carefully controlled laser diagnostics. The spatial distributions of soot volume fraction and the pulverized coal particles were measured simultaneously by laser induced incandescence (LII) and Mie scattering imaging, respectively. In addition, the radial distributions of the soot volume fraction were compared with the OH radical fluorescence, gas temperature and oxygen concentration obtained in our previous studies [1], [2]. The results indicated that the laser pulse fluence used for LII measurement should be carefully controlled to measure the soot volume fraction in pulverized coal flames. To precisely measure the soot volume fraction in pulverized coal flames using LII, it is necessary to adjust the laser pulse fluence so that it is sufficiently high to heat up all the soot particles to the sublimation temperature but also sufficiently low to avoid including a too large of a change in the morphology of the soot particles and the superposition of the LII signal from the pulverized coal particles on that from the soot particles. It was also found that the radial position of the peak LII signal intensity was located between the positions of the peak Mie scattering signal intensity and peak OH radical signal intensity. The region, in which LII signal, OH radical fluorescence and Mie scattering coexisted, expanded with increasing height above the burner port. It was also found that the soot formation in pulverized coal flames was enhanced at locations where the conditions of high temperature, low oxygen concentration and the existence of pulverized coal particles were satisfied simultaneously.     

Representations of (α, β, γ) triple system

We introduce a notion of (α, β, γ) triple system which generalizes the familiar generalized Jordan triple system. We then discuss its realization by some bilinear algebras and vice versa. We also give a characterization of the structurable algebra of Allison in terms of (?1, 1) Freudenthal–Kantor triple system by imposing some additional triple product constraints.     

Structure and stability of a homologous series of tin oxides

The structures and stabilities of a series of nonstoichiometric SnO2-x compounds, which are yet unknown experimentally, are predicted using the cluster expansion technique combined with first-principles calculations. A homologous series of Sn(n+1)O(2n) in which oxygen vacancies are layered on (101) planes of the rutile lattice is discovered. The homologous crystals are composed of divalent and quadrivalent Sn atoms. No trivalent Sn atoms are formed.     

Construction of a High‐Mannose‐Type Glycan Library by a Renewed Top‐Down Chemo‐Enzymatic Approach

A comprehensive method for the construction of a high‐mannose‐type glycan library by systematic chemo‐enzymatic trimming of a single Man9‐based precursor was developed. It consists of the chemical synthesis of a non‐natural tridecasaccharide precursor, the orthogonal demasking of the non‐reducing ends, and trimming by glycosidases, which enabled a comprehensive synthesis of high‐mannose‐type glycans in their mono‐ or non‐glucosylated forms. It employed glucose, isopropylidene, and N‐acetylglucosamine groups for blocking the A‐, B‐, and C‐arms, respectively. After systematic trimming of the precursor, thirty‐seven high‐mannose‐type glycans were obtained. The power of the methodology was demonstrated by the enzymatic activity of human recombinant N‐acetylglucosaminyltransferase‐I toward M7–M3 glycans, clarifying the substrate specificity in the context of high‐mannose‐type glycans.