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Electron spin resonance has been observed for Fe3+ and Mn2+ ions occupying sites with trigonal symmetry in undoped and doped Verneuil-grown crystals of the ilmenite type compound MgTiO3. At 300 K, the fine structure parameters in the spin Hamiltonian are (in 10?4cm?1) D = +844 (± 1), (a? F) = +118 (± 1), a = 69 (± 7) for Fe3+ and D = +164 (± 1), (a ? F) = +10.2 (± l), a = 7.0 (± 1) for Mn2+. These values are compared with literature data for Fe3+ and Mn2+ in other oxides, especially Al2o3, with particular reference to the recent “superposition” theory of the effect of a trigonal distortion. From the orientation of the axes of cubic pseudosymmetry of the spin Hamiltonian, and with the assumption that a has the same sign for both ions, it is proposed that Fe3+ and Mn2+ occupy the same octahedral site, namely the Mg2+ site. Anomalous line splittings observed for one sample were attributed to twinning on (0001) or {1120} planes. 相似文献
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Jacqueline Jiménez Mildred López Vladimir Carranza Angel Mendoza Jenaro Varela Estibaliz Sansinenea Aurelio Ortiz 《Tetrahedron letters》2017,58(3):235-239
An alternative methodology for the synthesis of chiral 3-(p-tolyl) butanoic acids is presented. This was accomplished through the diastereoselective hydrogenation reaction of different chiral N-3-(p-tolyl) but-2-enamides, using Pd/C in EtOH, to produce the corresponding chiral N-3-(p-tolyl) butanamides with high chemical yields and moderate diastereomeric ratios. Removal of the chiral auxiliary from N-3-(p-tolyl) butanamides gave the respective enantiomerically pure acids. 相似文献
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Conservative methods for the Toda lattice equations 总被引:1,自引:0,他引:1
We are concerned with the numerical integration of the Todalattice equations by using different conservative methods. Numericalexperiments suggest that the global error for isospectral schemesdecreases exponentially with time but it is almost constantfor either symplectic or more general integrators. We providea theoretical explanation for these experimental findings. 相似文献
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