Normal Coordinate Analysis of Pyridine-N-Oxide

We have been interested for some time in the study of the hydrogen bonded complexes in the far-infrared region with special attention to the adducts between phenol and pyridine-N-oxides (1). In such systems the intermolecular mode vσ was identified and some intramolecular vibrations related to the N-O group were observed to be remarkably shifted consequent on hydrogen bonding. In this context we wished to obtain a force field for the complex which could fit the observational results. Unfortunately for one of the constituents i. e. pyridine-N-oxide a force field, suitable for our purposes, was not available and therefore preliminarily we determined it. We report here the results of such analysis.     

Spectral Properties of Amphiflavins in Polymer Matrices

The parameters characterizing the absorption, fluorescence and phosphorescence of 10-dodecylisoalloxazine (DIA), 10-octadecylisoalloxazine (OIA) 3-methyl-10-dodecylisoalloxazine (MDIA) embedded into polymeric matrices (polystyrene – PS, polymethacrylate methyl – PMM and poly(vinyl alcohol) – PVA) were studied. It was found that both the polarity of microenvironment and its structure influenced the changes of the spectral properties of the examined amphiflavins.     

Teil III. Edelgasdetektoren,Indirekter Elektron-Mobility-Detektor und Schlußfolgerungen

Die Multiplikation von Ladungsträgern durch feldbeschleunigte Elektronen erfolgt im Bereich der unselbständigen Entladung. Sie wurde von Lovelock [1] erstmals für β-Argondetektoren zur Steigerung der Empfindlichkeit E_N angewandt. Detektoren im Bereich der selbständigen Entladung [2] haben sich nicht bewährt.     

Spectral,electron microscopic and chemical investigations of gamma-induced purple color zonings in amethyst crystals from the Dursunbey-Balıkesir region of Turkey

Amethyst crystals on matrix specimens from the Dursunbey-Bal?kesir region in Turkey have five representative purple color zonings: dark purple, light purple, lilac, orchid, and violet. The purple color zonings have been analyzed with optical absorption spectra in the visible wavelength region, chemical full trace element analyses (inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectroscopy), and scanning electron microscopic images with high magnification. It can be proposed that the production of the purple color in amethyst crystals is due to three dominant absorption bands centered at 375, 530, and 675 nm, respectively. In addition, the purple color zonings are also due to four minor absorption bands centered at 435, 480, 620, and 760 nm. X-ray diffraction graphics of the investigated amethyst crystals indicate that these crystals are composed of a nearly pure alpha-quartz phase and do not include any moganite silica phase and/or other mineral implications. Trace element analyses of the amethyst crystals show five representative purple color zonings, suggesting that the absorption bands can be mainly attributed to extrinsic defects (chemical impurities). However, another important factor that influences all structural defects in amethyst is likely to be the gamma irradiation that exists during amethyst crystallization and its inclusion in host materials. This gamma irradiation originates from the large underlying intrusive granitoid body in the region of amethyst formation. Irradiation modifies the valence values of the impurity elements in the amethyst crystals. It is observed that the violet-colored amethyst crystals have the most stable and the least reversible coloration when exposed to strong light sources. This situation can be related to the higher impurity content of Fe (2.50 ppm), Co (3.1 ppm), Ni (38 ppm), Cu (17.9 ppm), Zn (10 ppm), Zr (3.9 ppm), and Mo (21.8 ppm).     

Theoretical explanation of optical absorption spectra and covalent effect of Ni2+ ions in octahedral sites of Ca3Sc2Ge3O12 crystal

The optical absorption spectra (d-d transition bands) and covalent effect of Ni²⁺ ions in octahedral sites of Ca₃Sc₂Ge₃O₁₂ crystal have been investigated by the full energy matrix based on the two spin–orbit coupling parameters model. The bond length of octahedral site is R_i?=?2.19 Å, which can be determined by the cubic crystal-field parameter and optical spectral data. The lattice distortion of the Ni²⁺ center in Ca₃Sc₂Ge₃O₁₂ crystal is also obtained from the calculations. In addition, the result has shown that the covalent effect of Ni²⁺ ion in the octahedral site of Ga₃Sc₂Ge₃O₁₂ is obvious and cannot be ignored. The calculated d-d transition bands agree well with that of the experimental findings, suggesting that the present methods can explain reasonably the optical spectral data and covalent effect of 3d⁸ ions in octahedral lattices.     

Radiation hardness of gas discharge tubes and avalanche diodes used for transient voltage suppression

The widespread use of gas discharge tubes (GDTs) and avalanche diodes for transient voltage suppression (TVS) in many cases results in their exposure to ionizing radiation. The aim of this paper is to investigate the influence of irradiation on these TVS devices’ characteristics, by exposing them to a combined neutron/gamma radiation field. Experimental results show that irradiation of TVS diodes causes a lasting degradation of their protective characteristics. On the other hand, GDTs exhibit a temporary change of performance. The observed effects are presented with the accompanying theoretical interpretations, based on the interaction of radiation with materials constituting the investigated devices.     

Color centers in irradiated MgF2

Abstract

Color centers in rutile-structured MgF₂ single crystals irradiated at 20K/360K by reactor neutrons are investigated spectroscopically at LNT. Four different types of the F-F vacancy bond in MgF₂ are possibly identified to the observed absorption bands as due to the F₂ centers; instead of previous assignments, the 300nm band to the F₂(D_2h), the 325nm band to the F₂(C₁), the 355nm band to the F₂(C_2v), and the 400nm band to the F₂(C_2h) centers.     

Microplasma Technology and Its Applications in Analytical Chemistry

Abstract

This review article describes some existing microplasma sources and their applications in analytical chemistry. These microplasmas mainly include direct current glow discharge (DC), microhollow-cathode discharge (MHCD) or microstructure electrode (MSE), dielectric barrier discharge (DBD), capacitively coupled microplasmas (CCμPs), miniature inductively coupled plasmas (mICPs), and microwave-induced plasmas (MIPs). The historical development and recent advances in these microplasma techniques are presented. Fundamental properties of the microplasmas, the unique features of the reduced size and volume, as well as the advantageous device structures for chemical analysis are discussed in detail, with the emphasis toward detection of gaseous samples. The analytical figures of merit obtained using these microplasmas as molecular/elemental-selective detectors for emission spectrometry and as ionization sources for mass spectrometry are also given in this review article.     

Pressure-induced non-linear optical properties in a wurtzite GaN/Al x Ga1− x N strained quantum dot

The effects of hydrostatic pressure on the exciton ground-state binding energy and the interband emission energy in a GaN/Al _x Ga_{1??? x} N quantum dot are investigated. The effects of strain and the internal field due to spontaneous and piezo-electric polarizations are included in the Hamiltonian. Numerical calculations are performed using variational procedure within the framework of single-band effective-mass approximation. The dependence of non-linear optical processes on the dot sizes is brought out in the influence of pressure. Pressure-induced optical properties are obtained using the compact density matrix approach. The effects of hydrostatic pressure on the linear, third-order non-linear optical absorption coefficients and the refractive index changes of the exciton as a function of photon energy are calculated. Our results show that the effects of pressure and the geometrical confinement have great influence on the optical properties of GaN/Al _x Ga_{1??? x} N dot.     

水中孤立气泡对声波的耗散作用

本文从气泡壁面线性运动方程出发,对水中孤立气泡的声耗散机理进行了分析。结果表明:气泡对声波具有明显的耗散作用;耗散作用由声散射和声吸收两部份组成;热传导在气泡对声波的耗散作用中起决定性作用;气泡处于谐振时,对声波具有最大的耗散作用。