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11.
12.
S V Deshmukh 《Pramana》1978,11(6):755-760
The effect of Gaunt factor correction on temperature estimation over a range 100 to 1500 eV had been studied. Greene’s analytical
expression for the quantum mechanical Gaunt factor averaged over Maxwellian distribution is used. Transmission ratios are
calculated with and without Gaunt factor for various combinations of beryllium foils, taking into account x-ray emission due
to free-free transitions. A significant difference (≳ 15%) is observed between the temperatures estimated from classical and
quantum mechanical curves, above 600 eV. Selection of foil combinations useful for estimating higher temperatures is also
discussed. 相似文献
13.
The channelling of protons through a thin beryllium crystal is simulated in a computer. The angular dependence of the momentum
density is computed using particle trajectory approximation and is reported as the transmission spectra. In obtaining the
spectra, the energy loss suffered by protons due to electron multiple scattering is considered and the effect of thermal vibrations
treated separately. The spectra obtained are characteristic of the hcp structure of Be. Positions of the major dips in the
transmission spectra are found to correlate well with the directions of neighbouring strings. Variations in the angle of incidence
of the beam and in its initial azimuthal angle bring about modifications in the spectra depending on the transverse kinetic
energy of the incident particles and the crystalline structure of Be. Thermal vibration of the lattice does not modify the
spectra appreciably. 相似文献
14.
15.
Dr. Florian Kraus Dipl.‐Chem. Sebastian A. Baer Dr. Magnus R. Buchner Dr. Antti J. Karttunen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(7):2131-2142
The first structural characterization of the text‐book tetraammineberyllium(II) cation [Be(NH3)4]2+, obtained in the compounds [Be(NH3)4]2Cl4 ? 17NH3 and [Be(NH3)4]Cl2, is reported. Through NMR spectroscopic and quantum chemical studies, its hydrolysis products in liquid ammonia were identified. These are the dinuclear [Be2(μ‐OH)(NH3)6]3+ and the cyclic [Be2(μ‐OH)2(NH3)4]2+ and [Be3(μ‐OH)3(NH3)6]3+ cations. The latter species was isolated as the compound [Be3(μ‐OH)3(NH3)6]Cl3 ? 7NH3. NMR analysis of solutions of BeF2 in liquid ammonia showed that the [BeF2(NH3)2] molecule was the only dissolved species. It acts as a strong fluoride‐ion acceptor and forms the [BeF3(NH3)]? anion in the compound [N2H7][BeF3(NH3)]. The compounds presented herein were characterized by single‐crystal X‐ray structure analysis, 9Be, 17O, and 19F NMR, IR, and Raman spectroscopy, deuteration studies, and quantum chemical calculations. The extension of beryllium chemistry to the ammine system shows similarities but also decisive differences to the aquo system. 相似文献
16.
17.
简述了BeH2材料的制备方法、结构形式和物理化学性质,并分析了其在惯性约束聚变(ICF)中的应用。BeH2材料主要由二叔丁基铍热解法和元素化学气相沉积法制备,其纯度(质量分数)高达99%。非晶BeH2材料的结构是一种共用氢原子作为顶点的BeH4四面体网络结构。非晶BeH2材料不仅具有铍的优点,还具有聚合物的优点,作为ICF靶可以降低瑞利-泰勒不稳定性,而且掺入高Z元素后还可以降低D-T燃料的预热。非晶BeH2材料作为烧蚀层,掺入高Z元素后可以提高激光-X光的转换效率。 相似文献
18.
Holger Braunschweig Prof. Dr. Katrin Gruss Krzysztof Radacki 《Angewandte Chemie (International ed. in English)》2009,48(23):4239-4241
A platinum–beryllium adduct (see structure) was prepared by the reaction of [Pt(PCy3)2] and BeCl2. Treatment with methyllithium resulted in ligand substitution at the beryllium center. Both complexes were structurally characterized and display unprecedented two‐center two‐electron bonds between a transition metal and beryllium.
19.
del Mar Conejo M Fernández R del Río D Carmona E Monge A Ruiz C Márquez AM Sanz JF 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(18):4452-4461
The beryllocenes [Be(C(5)Me(4)H)(2)] (1), [Be(C(5)Me(5))(2)] (2), and [Be(C(5)Me(5))(C(5)Me(4)H)] (3) have been prepared from BeCl(2) and the appropriate KCp' reagent in toluene/diethyl ether solvent mixtures. The synthesis of 1 is facile (20 degrees C, overnight), but generation of decamethylberyllocene 2 demands high temperatures (ca. 115 degrees C) and extended reaction times (3-4 days). The mixed-ring beryllocene 3 is obtained when the known [(eta(5)-C(5)Me(5))BeCl] is allowed to react with K[C(5)Me(4)H], once more under somewhat forcing conditions (115 degrees C, 36 h). The structures of the three metallocenes have been determined by low-temperature X-ray studies. Both 1 and 3 present eta5/eta1 geometries of the slip-sandwich type, whereas 2 exhibits an almost regular, ferrocene-like, sandwich structure. In the mixed-ring compound 3, C(5)Me(5) is centrally bound to beryllium and the eta(1)-C(5)Me(4)H ring bonds to the metal through the unique CH carbon atom. This is also the binding mode of the eta(1)-ring of 1. To analyze the nature of the bonding in these molecules, theoretical calculations at different levels of theory have been performed on compounds 2 and 3, and a comparison with the bonding in [Be(C(5)H(5))(2)] has been made. As for the latter molecule, energy differences between the eta5/eta5 and the eta5/eta1 structures of 2 are very small, being of the order of a few kcal mol(-1). Constrained space orbital variations (CSOV) calculations show that the covalent character in the bonding is larger for [Be(C(5)Me(5))(2)] than for [Be(C(5)H(5))(2)] due to larger charge delocalization and to increased polarizability of the C(5)Me(5) fragment. 相似文献
20.
Masataka Hiraide Kennich Ishikawa Zuo Sheng Chen Hiroshi Kawaguchi 《Mikrochimica acta》1994,117(1-2):7-13
Coprecipitation first with magnesium hydroxide, next with tin(IV) hydroxide is developed for the determination of traces of beryllium in sea-water. To a 200-ml sample is added a sodium hydroxide solution to form magnesium hydroxide at pH 11.5, on which beryllium is quantitatively coprecipitated. The precipitate is separated by centrifugation and dissolved in 2 ml of 12 mol/l hydrochloric acid. The resulting solution (ca. 10 ml) is mixed with 2 mg of tin (IV) carrier and the pH is adjusted to 5.0 to collect the beryllium on tin (IV) hydroxide, leaving magnesium ions in the solution. The tin (IV) hydroxide is centrifuged, dissolved in 0.1 ml of 5 mol/l hydrobromic acid, and then diluted to 1 ml with water. Magnesium is so added as to be 500 g/ml for increasing the sensitivity about four times, and the beryllium in the solution is determined by graphite furnace atomic absorption spectrometry. The experiments with synthetic seawater samples showed that pg — g amounts of beryllium can be coprecipitated on the metal hydroxides and beryllium at the low ng/1 level can be determined with reasonable precision (RSD < 10%). The detection limit of the proposed method is 0.5 ng/l of beryllium in seawater. 相似文献