Crystallinity, field sample

Figure 4 shows typical IR absorption spectrum of an as-grown HT ZnO sample. The lines at 4216.2, 4240.0, and 4246.6 cm were previously identified as internal transitions of substitutional Ni split by the local crystalline field.The new lines at 3335.6, 3482.9, 3516.3, and 3577.3 cm are located in the region characteristic of 0-H stretch modes. 

Entropy evaluations from published cryothermal data on the lanthanide (III) oxides are summarized in Table II with an indication of the lowest temperature of the measurements and the estimated magnetic entropy increments below this temperature. Their original assignment of crystalline field levels from thermal data still appears to be in good accord with recent findings e.g., 17). Unfortunately, measurements on these substances were made only down to about 8°K. because the finely divided oxide samples tend to absorb the helium gas utilized to enhance thermal equilibration between sample and calorimeter. 

The orientational dependence is present in the chemical shielding tensor which in its principal axis system (PAS) is diagonal with principal components axx, o yy and ctzz-In a crystalline powder sample all orientations of the PAS system of the shielding tensor are present and for most orientations the PAS does not coincide with the laboratory (LAB) frame where the z-axis is aligned with the direction of the applied magnetic field Bq. Hence the tensor representation gives in the PAS... 

Despite their highly successful record, MD or MC simulations are still hardly extended to the direct interpretation of complex set-ups, typical of most rheological experiments. In such cases it is preferable to employ mean-field or continuum descriptions, based of the numerical solution of the constitutive equations describing hydrodynamic properties. Such techniques were for instance applied to the prediction of transient director patterns of liquid crystalline nematic samples [11-14]. Hydrodynamic treatments are algebraically complex and computationally intensive, and their implementation is limited mostly to nematic phases. 

The spectra of NF2 in Ar matrices at 4.2 K were compared for two different mole ratios of matrix-to-radical precursor, M/R = 300 and 1200 (deposition of room-temperature equilibrium mixtures of N2F4/NF2 and matrix gas onto a liquid helium cooled sapphire rod). The M/R = 300 sample gave an approximately axially symmetric g tensor indicating nearly free rotation of the NF2 radical about an axis perpendicular to the molecular plane (x axis, see below). The more diluted sample (M/R = 1200) unexpectedly exhibited the spectrum of a randomly oriented radical with three different principal values for the g tensor this may be due to a stronger crystalline field effect. The spectrum of NF2 in Kr at 4.2 K (M/R = 300) indicated freer rotation than in Ar with M/R = 300. At about 30 K the completely resolved isotropic triplet set of triplets of an almost freely rotating NF2 radical was observed in the Ar and Kr matrices [6, 7]. With CCI4 as the matrix material, somewhat distorted spectra were observed at 4.2 to 30 K [6]. 

In chapter 114, O. Vogt and K. Mattenberger examine the magnetic behaviors of the lanthanide and actinide Bl, NaCl-type structures. The magnetic properties of a sample depend upon the spectroscopic state of the f-element and the possibility of J-mixing, the electric crystalline field, the exchange interactions and hybridization. The competition between these various factors can make the materials complicated or simple with respect to their magnetic behaviors. 

WAXS measurements were taken at the different orientation of film position relative to X-ray irradiation beam. For all samples, the dififracto-grams reveal the existence of axial cylindrical texture in PVA. The axis of texture coincides with extrusion direction, and hence the PVA molecules in quasi-crystalline fields oriented along extrusion direction. In samples with 10 and 20 wt.% of PHB a well-defined axial texture of PHB crystallites is evident, where the texture axis coincides with direction of extrusion as well. However, the PHB crystallites oriented relative to the texture axes so that the extrusion direction in line with the axis a of elementary crystalline cell. Hence, the axes of PHB molecules are normally oriented relative to extrusion direction. 

Obtaining high-quality nanocry stalline samples is the most important task faced by experimentalists working in tire field of nanoscience. In tire ideal sample, every cluster is crystalline, witli a specific size and shape, and all clusters are identical. Wlrile such unifonnity can be expected from a molecular sample, nanocrystal samples rarely attain tliis level of perfection more typically, tliey consist of a collection of clusters witli a distribution of sizes, shapes and stmctures. In order to evaluate size-dependent properties quantitatively, it is important tliat tire variations between different clusters in a nanocrystal sample be minimized, or, at tire very least, tliat tire range and nature of tire variations be well understood. 

This configuration has not yet been demonstrated by X-ray studies, perhaps due to the difficulty in obtaining good crystalline samples. Recently, Tzschach reviewed the whole field of intramolecularly pentacoordinate, organotin compounds (198), including the stannatranes. 

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