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71.
Electron spin resonance investigations of Gd3+ ions in YBa2Cu3O7?δ give distinct indications for an exchange coupling of these paramagnetic ions to the doped charge carriers and allow the corresponding interaction parameters, as well as the mutual Gd-Gd exchange coupling, to be extracted. 相似文献
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73.
Hydrolysis of Bi(NO(3))(3) in aqueous solution gave crystals of the novel compounds [Bi(6)O(4)(OH)(4)(NO(3))(5)(H(2)O)](NO(3)) (1) and [Bi(6)O(4)(OH)(4)(NO(3))(6)(H(2)O)(2)]·H(2)O (2) among the series of hexanuclear bismuth oxido nitrates. Compounds 1 and 2 both crystallize in the monoclinic space group P2(1)/n but show significant differences in their lattice parameters: 1, a = 9.2516(6) ?, b = 13.4298(9) ?, c = 17.8471(14) ?, β = 94.531(6)°, V = 2210.5(3) ?(3); 2, a = 9.0149(3) ?, b = 16.9298(4) ?, c = 15.6864(4) ?, β = 90.129(3)°, V = 2394.06(12) ?(3). Variation of the conditions for partial hydrolysis of Bi(NO(3))(3) gave bismuth oxido nitrates of even higher nuclearity, [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·4DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·4DMSO] (3) and [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·2DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·0.5DMSO] (5), upon crystallization from DMSO. Bismuth oxido clusters 3 and 5 crystallize in the triclinic space group P1? both with two crystallographically independent molecules in the asymmetric unit. The following lattice parameters are observed: 3, a = 20.3804(10) ?, b = 20.3871(9) ?, c = 34.9715(15) ?, α = 76.657(4)°, β = 73.479(4)°, γ = 60.228(5)°, V = 12021.7(9) ?(3); 5, a = 20.0329(4) ?, b = 20.0601(4) ?, c = 34.3532(6) ?, α = 90.196(1)°, β = 91.344(2)°, γ = 119.370(2)°, V = 12025.8(4) ?(3). Differences in the number of DMSO molecules (coordinated and noncoordinated) and ligand (nitrate, DMSO) coordination modes are observed. 相似文献
74.
Reactions of Ti(OiPr)4 with different phosphonic acids RPO3H2 (R = Ph, 4-CNPh, Me, tBu) in organic solvents have been investigated. In the presence of small amounts of water, the new molecular titanium oxide alkoxide phosphonates [Ti4(mu 3-O)(OiPr)5(mu-OiPr)3(RPO3)3].DMSO [R = Ph (1), Me (2), tBu (3), 4-CNPh (4)] were isolated. The single-crystal X-ray structure analyses of 1 and 2 revealed hexacoordinated titanium atoms and a connectivity of (111) for each phosphonate. Under rigorous exclusion of water, the reaction of Ti(OiPr)4 with tert-butylphosphonic acid in toluene gave the titanium phosphonate tetramer [Ti(OiPr)2(tBuPO3)]4 (5). A single-crystal X-ray structure analysis of 5 revealed a 5 + 1 coordination of the titanium atoms as a result of the (112) connectivity of each phosphonate; such a coordination mode has never been reported for a titanium phosphate, phosphonate, or phosphinate. Compounds 1-5 were characterized by FT-IR, 31P MAS NMR, and solution multinuclear NMR (1H, 13C(1H,) 31P(1H)) spectroscopies. 13C CP MAS NMR experiments were carried out on arylphosphonates 1 and 4. Solution NMR experiments were also used to investigate the exchange reaction between 1 and 2 and the conversion of 5 to [Ti4(mu 3-O)(OiPr)5(mu-OiPr)3(tBuPO3)3].iPrOH by partial hydrolysis in the presence of Ti(OiPr)4. The phosphonate clusters 1-5 are soluble in organic solvents and are likely intermediates in the sol-gel processing of inorganic-organic hybrids based on titanium oxide and phosphonate groups that we are currently developing. 相似文献
75.
We present a number of techniques which may be used to obtain precise values of selective spin-spin interactions between two nuclear spins in a hostile environment. Such an environment may be characterized by very fast relaxation and decoherence, e.g. due to the strong coupling of the two spins of interest to electron spins in their vicinity as well as other nuclei. Here, we used dilute paramagnetic Ce(3+) centers hosted in a single crystal of CaF(2). Selected (19)F internuclear interactions were measured indirectly by applying different electron nuclear double resonance (ENDOR) pulse sequences. 相似文献
76.
de Swiet TM Yarger JL Wagberg T Hone J Gross BJ Tomaselli M Titman JJ Zettl A Mehring M 《Physical review letters》2000,84(4):717-720
We present high resolution 133Cs-13C double resonance NMR data and 13C-13C NMR correlation spectra of 13C enriched samples of the polymeric phase of CsC60. These data lead to a partial assignment of the lines in the 13C NMR spectrum of CsC60 to the carbon positions on the C60 molecule. A plausible completion of the assignment can be made on the basis of an ab initio calculation. The data support the view that the conduction electron density is concentrated at the C60 "equator," away from the interfullerene bonds. 相似文献
77.
We describe a rotation sensor that is based on the detection of the nuclear magnetic resonance signal of129Xe in the gas phase. Under rotation shifts of the signal phase and Larmor frequency occur, which can be used to determine orientational angle variations with an accuracy of about 1o and rotation rates of 0.4 mHz to 5 Hz with a precision of 0.4 mHz during the measurement time, which is of the order of 3×T 2, the nuclear spin relaxation time. The nuclear spin species is polarized by spin-exchange collisions with optically pumped ground-state spins of Rb-gas atoms. The Rb atoms also present in the sample are used as a magnetometer to probe the free-induction decay of the nuclear spin ensemble. Polarization, detection, and data processing sheemes are described in detail and the current sensitivity and limitations of this Stuttgart nuclear magnetic resonance (NMR) gyroscope are discussed. Possibilities for further improvements are pointed out. 相似文献
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80.
The proton chemical shift tensor in squaric acid, which undergoes an antiferrodistortive phase transition at Tc = 97°C, has been determined by means of a multiple-pulse NMR experiment. No change of the shift tensor is observed, when going through the phase transition, indicating a purely order—disorder type transition. The principal values of the shift tensor are: — 26.5, —20.2 and 1.0 ppm with respect ti TMS. 相似文献