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931.
The signs of dipole moment derivatives for ethylene oxide obtained from ab initio calculations using the 6-31G1 basis set are presented. From these signs and the experimental vibrational absorption intensity data, the atomic polar tensor elements and bond charge flux parameters were evaluated. These quantities were compared with those in the literature calculations employing approximate signs and force constants. 相似文献
932.
933.
Dipl.-Phys. W. R. Hess Prof. Dr. J. Brandmüller 《Zeitschrift für Physik A Hadrons and Nuclei》1969,224(1-3):144-147
A perturbation calculation is used to determine the effect of intermolecular interactions on the depolarization ratio of Raman lines. For highly polarized Raman lines an approximate formula is given, which enables the evaluation of the relative change of the anisotropy scattering using the change in the degree of depolarization. 相似文献
934.
935.
It is shown that the EPR linewidth spectrum of triplet excitons in molecular crystals can be severely distorted by weak orientational disorder. The demonstration employs a one-parameter correction procedure based on the assumption that the angular dependence of excess width is directly proportional to the angular gradient of the resonant field. Application to the discrepant data of Haarer and Wolf brings them into agreement with theory and with more recent experiments. A phenomenological model of the disorder is used to interpret the distortion parameter. These results suggest the potential value of exciton EPR as a probe of structural imperfections in molecular crystals. 相似文献
936.
937.
938.
A certain "critical" molecular weight controls rheological properties of the multibead finitely extensible nonlinear elastic (FENE) chain model polymer melt. The rheological crossover manifests itself in a change of power law behavior for the viscous properties at a critical number of beads per chain N(c) = 100+/-10. This finding confirms a newly proposed relationship between dimensionless critical weight, characteristic length, and flexibility which we obtain as a side result. Results further suggest that the entanglement molecular weight N(e) for the flexible FENE chain model could be comparable in size or even larger than its critical molecular weight N(c). 相似文献
939.
The characteristic features and applications of linear and nonlinear guided elastic waves propagating along surfaces (2D) and wedges (1D) are discussed. Laser-based excitation, detection, or contact-free analysis of these guided waves with pump–probe methods are reviewed. Determination of material parameters by broadband surface acoustic waves (SAWs) and other applications in nondestructive evaluation (NDE) are considered. The realization of nonlinear SAWs in the form of solitary waves and as shock waves, used for the determination of the fracture strength, is described. The unique properties of dispersion-free wedge waves (WWs) propagating along homogeneous wedges and of dispersive wedge waves observed in the presence of wedge modifications such as tip truncation or coatings are outlined. Theoretical and experimental results on nonlinear wedge waves in isotropic and anisotropic solids are presented. 相似文献
940.
Fabrication of surfaces with heterogeneous contact angle hysteresis enables extraction of droplet samples from bulk liquid volumes. These surfaces are created by printing high hysteresis wax islands onto low hysteresis superhydrophobic paper. The volume of the sampled droplets depends on the hysteresis of the printed islands, which can be controlled through both physical and chemical means. Physically, hysteresis is modified through the addition of surface roughness. Chemical hysteresis is tuned by changing the active chemical groups present on the wax surface. The observed control of the volume of sampled droplets, which is necessary for quantitative biochemical or chemical assays, extends to scenarios in which multiple droplet samples are extracted simultaneously from a single bulk droplet. Demonstration of the capacity of this technique to perform colorimetric glucose immunoassays is described. The ability to obtain well-defined microliter sample volumes and to extract several samples simultaneously from the same source enables the development of two-dimensional paper-based microfluidic devices for biomedical testing. 相似文献