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101.
When alkali-metals such as Li, Na, K, Rb and Cs were adsorbed on clean Si(111) 7 × 7 surface at room temperature, the intensity distribution of the original 7 × 7 RHEED pattern changes gradually with the increase of alkali-metal adsorption, and at last a new superstructure with 7 × 7 periodicity, here named δ-7 × 7 structure, has been observed. This change at room temperature can be explained if the 7 × 7 structure is mostly made of displacement. The structure model estimated from the intensity distribution of the δ-7 × 7 pattern is the one that has one vacancy at the corners of the 7 × 7 unit mesh and relaxed surrounding atoms. The change of the 7 × 7 structure by alkali-metal adsorption to this model is naturally understood with our new model (1984). For all alkali metals, by adsorption at high temperature 3 × 1 superstructure has also been observed for the first time. 相似文献
102.
Absolute configurations of axially chiral biaryls with hydroxyl, amino, and carboxyl groups can be easily determined by pmr spectra using MTPA derivatives and shift reagents. 相似文献
103.
104.
The basic conditions for the determination of niobium, titanium and zirconium with an argon plasma and a Hitachi UHF Plasma Spectrascan operated at 2450 MHz and 450 W maximum output, have been established. The niobium 405.89-nm, titanium 365.35-nm and zirconium 339.19-nm lines gave detection limits of 0.5, 0.1 and 2.0 p.p.m., respectively, when pure solutions were used. Effects of gas flow rates, high-frequency output and concentration of acids were examined. In applications to steel, titanium was determined without prior chemical separation from iron at the 499.95-nm line, whereas niobium and zirconium could not be determined in the presence of large amounts of iron. When a cupferron precipitation method followed by extraction of iron with methyl isobutyl ketone was applied, satisfactory results were obtained. 相似文献
105.
Youichi Ohno Katsuichi Kaneda Shozo Okada Kimiaki Hirama 《Journal of solid state chemistry》1984,54(2):170-178
The sulfur K and metal LIII absorption spectra of transition-metal trichalcogenides (TMTC's) were measured. The matrix element effect plays an important role in these spectra. It was considered that the structures up to 5 eV above the absorption edge reflect the chalcogen antibonding band, the metal nonbonding dz2 band, and the metal d bands, and that the higher energy structures are derived from the metal s and p bands. The chalcogen antibonding band arises from chalcogen pairing and the metal d, s, and p bands are the mixture bands with chalcogen p orbitals. Evidence that shows that the lowest conduction band of the group IV TMTC's is the chalcogen antibonding band is presented. The overlap of the metal d and metal s bands is promoted by increasing the atomic number of chalcogen atoms. 相似文献
106.
Cadmium(II) reacts with 2-[2-(5-bromopyridyl)azo]-5-dimethyl-aminophenol (5-Br-DMPAP) in aqueous solution; the complex can be extracted with organic solvents such as chloroform, 3-methyl-l-butanol and methyl isobutyl ketone at pH 8–10.5 to give a red solution which absorbs at 525–555 nm. The absorbance in organic solvents is stable and the system conforms to Beer's law; the optimal range in 3-methyl-1-butanol for measurement in 1.00-cm cells is 0.01–l p.p.m. cadmium. Moderate amounts of many cations and anions do not interfere, and interfering cations such as zinc, copper, manganese and nickel can be separated by extraction with dithizone. The 5-Br-DMPAP method is one of the most sensitive procedures available for the determination of cadmium; the molar absorptivity in a 3-methyl-1-butanol extract is 1.41·105 1 mol?1 cm?1 at 555 nm. 相似文献
107.
Shozo Shibata Masamichi Furukawa Eijiro Kamata Kazuo Goto 《Analytica chimica acta》1970,50(3):439-446
The heterocyclic azo compound, 1-[(5-chloro-2-pyridyl)azo]-2-naphthol (5-Cl-β-PAN), forms various coloured metal chelates, which can be extracted with different organic solvents. Chelate stability is greatly affected by pH. The molar absorptivities are usually considerably greater than those of the β-PAN chelate. Although the bathochromic shifts produced on chelation are no greater than those with 5-Br-β-PAN, the selectivity is increased. The reactivity of tri- and tetravalent metal ions is decreased appreciably by introduction of the chlorine. A correct choice of pH, solvent and masking reagent allows 5-C1-β-PAN to be made reasonably selective. 相似文献
108.
1-(2-Pyridylazo)-2-naphthol (PAN) rcacts with uranium to form a deep red precipitate in ammoniacal solutions, this can be extracted with chloroform if sodium chloride or sulfate is added and it has a maximum absorption at 560 mμ The color is stable and follows Beer's law. Trace amounts of uranium may be determined in the presence of many metals without prior separation if strong complexing agents, such) as EDTA or cyanide, are added 相似文献
109.
Summary A highly sensitive and selective Spectrophotometric method has been developed for the determination of yttrium in aluminium base alloys. The method is based on the red water-insoluble complex formed when yttrium and 1-[(5-methyl-2-pyridyl)azo]-2-naphthol (5-Me--PAN) react in a pH 9.5–11.2 solution. This complex could be extracted into ether (absorption maximum, 530 nm). Beer's law is obeyed up to 1 p. p. m. of yttrium and the molar absorptivity is 6.4 · 104 l · mole–1 · cm–1 at 530 nm.
Zusammenfassung Eine hochempfindliche und selektive spektrophotometrische Methode zur Bestimmung von Yttrium in Aluminiumlegierungen wurde ausgearbeitet. Sie beruht auf der Bildung der roten, wasserlöslichen Komplexverbindung des Yttriums mit 1-[(5-Methyl-2-pyridyl)azo]-2-naphthol(5-Me--PAN) bei pH 9,5–11,2. Diese Verbindung läßt sich mit Äther extrahieren und hat ein Absorptionsmaximum bei 530 nm. Das Beersche Gesetz ist bis zu 1 ppm Yttrium erfüllt. Die molare Extinktion beträgt 6,4 · 104 1 · Mol–1 cm–1 bei 530 nm.相似文献
110.
Naoki Inamoto Shozo Masuda Katsumi Tokumaru Masayuki Yoshida Youko Tamura Kazuo Tori 《Tetrahedron letters》1975,16(43):3697-3700