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21.
M. Moreno M. T. Barriuso J. A. Aramburu 《International journal of quantum chemistry》1994,52(4):829-835
Experimental results on 3d Oh complexes in insulators reveal that 10Dq α R?n, where R is the metal–ligand distance and n is close to five. This strong dependence determines the Huang–Rhys factor, S(A1g), associated to the symmetric A1g mode of the first excited state of complexes like MnX and CrX (X = halide) and makes it possible to measure R changes down to ∽ 10?3 Å. This work is devoted to understanding, within a molecular orbital framework, the microscopic origin of such a dependence, which is related to the corresponding one displayed by the transferred spin densities fσ, fs, and fπ. The analysis is focused on MnF. As a main result, it is shown that though fσ ? fs the interaction between d(eg) orbitals and 2s orbitals of F? is not only primarily responsible for the R dependence of 10Dq but also makes a significant contribution to the 10Dq value itself. The present work thus shows that the significant dependence of 10Dq upon R is ultimately related to the strong dependence of fs and the isotropic superhyperfine constant As upon R displayed by the experimental results of several 3d impurities. © John Wiley & Sons, Inc. 相似文献
22.
Marchán V Moreno V Pedroso E Grandas A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(4):808-815
We have studied how platinum(II) complexes [Pt(dien)Cl]Cl, [Pt(en)Cl2] and cisplatin react with hybrid molecules that contain sulfur and nitrogen ligands, in particular Phac-Met-linker-p5'dG (Phac = phenylacetyl), Phac-His-linker-p5'dG, Phac-His-Met-linker-p5'dG and Phac-His-Gly-Met-linker-p5'dCATGGCT. The progress of the reactions was monitored by HPLC, and by [1H,15N]-HSQC NMR when 15N-cisplatin was used. The products were isolated and characterised by using enzymatic and chemical reactions and spectroscopic techniques (UV and/or NMR spectroscopy, electrospray or MALDI-TOF mass spectrometry). The combined use of digestion with proteases and reaction with hydrogen peroxide followed by mass spectrometric analysis indicated the platinum coordination positions on the peptide moiety of the largest hybrid. Monofunctional Pt-S adducts were transformed into Pt-N complexes in which Pt-N7 bonds were formed preferentially. Most of the chelates isolated had Pt-S bonds, and, in the case of cisplatin complexes, loss of the ammine trans to sulfur gave rise to the formation of tricoordinate species with platinum-mediated peptide-nucleotide cross-links. 1,2-Intrachain platinum GpG adducts were only obtained in very small amounts (1-4%). 相似文献
23.
A kinetic method is described for the determination of trace amounts of manganese(II), based on its catalytic effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide. The reaction is followed by measuring the rate of change of fluorescence (lambda(ex) 365 and lambda(em) 440 nm). The calibration is linear over the manganese range 2-9 ng ml with a precision of +/-1%. The proposed method suffers from few interferences. 相似文献
24.
C.?GarciaEmail author A.?Durán R.?Moreno 《Journal of Sol-Gel Science and Technology》2005,34(3):211-217
Functional coatings incorporating different types of particles developed by the sol–gel method have been proposed in the last few years for diverse applications. This work focuses on the preparation of homogeneous coatings prepared from stable suspensions with 10 wt% of glass and glass ceramic particles in a hybrid organic–inorganic solution as dispersing media. For this purpose, the pH was shifted up to 6–7 by adding tetrapropylammonium hydroxide (TPAH) which behaves as a cationic surfactant being probably adsorbed on the particles surface, while the sol maintains stable. Rheological measurements were performed to study the stability of the suspensions prepared at different conditions such as the kind and concentration of dispersant and the pH conditions. After sintering at 450∘C/30 min, coatings around 2 μ m in thickness were obtained. 相似文献
25.
Inmaculada Beloso Paulo Prez‐Lourido Jesús Castro Jos A. García‐Vzquez Jaime Romero 《无机化学与普通化学杂志》2005,631(11):2101-2106
Heteroleptic nickel(II) complexes [NiL2L′] of a series of monoanionic and potentially bidentate N‐2‐pyridyl‐sulfonamide ligands [HL] and 2,2′‐bipyridine or 1,10‐Phenanthroline (L′) have been prepared by electrochemical oxidation of a nickel anode in an acetonitrile solution of the ligands. The complexes have been characterized by microanalysis, IR and electronic spectroscopy, magnetic measurements and LSI mass spectrometry. The crystal structure of [Ni(Ms6mepy)2(bipy)] has been determined by x‐ray diffraction and shows the metal in an octahedral NiN6 environment. Octahedral structures are also proposed for the other complexes with the N‐2‐pyridyl‐sulfonamide ligands acting as N,N′ or N, O bidentate systems, depending on the position of the methyl substituent on the pyridine ring. 相似文献
26.
J. C. Moreno J. Nilsen J. A. Koch B. J. MacGowan J. H. Scofield L. B. Da Silva 《Applied physics. B, Lasers and optics》1994,58(1):3-5
Neon-like niobium X-ray lasers have been studied using both slab and thin-foil target geometries. Niobium foils of various lengths were irradiated from both sides with two beams of the frequency-doubled Nova laser system using a line focus. We looked for gain by measuring spectrally integrated line intensities at different plasma lengths. Gain was observed in four neon-like niobium lines corresponding to 3s–3p transitions. The line profile of theJ = 0–1 line ( = 145.9 ) shows splitting due to the hyperfine effect. Improved contrast in the hyperfine structure is observed as the plasma length is increased. Hyperfine splitting may be relevant to other 3s–3p transitions in neon-like niobium as well as other neon-like X-ray laser systems. 相似文献
27.
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29.
J. Nilsen J. C. Moreno B. J. MacGowan J. A. Koch 《Applied physics. B, Lasers and optics》1993,57(5):309-311
We report lasing for the first time in nickel on the neon-like J=01, 3p3s transition at 231 Å as well as several weaker transitions including the J=2»1 lines at 298 Å and 304 Å. Amplification is seen only when the prepulse technique of using a low intensity prepulse before the main optical drive pulse is used to illuminate the nickel target. The prepulse technique is also shown to produce lasing in copper and dramatically improve the output of the germanium laser. 相似文献
30.