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Structures and Properties of LiF Cluster-assembled Nanofilms
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作者 Wang, GH Liu, FQ 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 1997年第4期274-279,共6页
We have studied structures and properties of nanostructured films prepared with nanometer-sized lithium fluoride (Lif) clusters by inert gas condensation method, and then characterized by transmission electron microsc... We have studied structures and properties of nanostructured films prepared with nanometer-sized lithium fluoride (Lif) clusters by inert gas condensation method, and then characterized by transmission electron microscope, Fourier transform infrared spectra and Raman scattering spectra, etc. Following important results are obtained: Multi-order-like Raman scatterings from LiF clusters are obtained, including the fine structure of the spectra. The observed Raman peaks are discussed in terms of surface optical modes, LO, TO, LA modes and their combination form. As the cluster size decreases, the phonons are confined in nanoscale so that the q vector selection rule is relaxed or even totally free of q conservation, and prohibition at the first- and third-order scatterings in the bulk LiF crystal is relaxed. The surface modes appear and play an important role in Raman scattering processes. The infrared absorption spectra are obtained with different deposition conditions. When the clusters are in the medium size range from similar to 7 to 15 nm, most infrared absorption peaks are second-order feature, and no single surface mode emerges. For the smaller clusters, molecular-like vibration is observed whereas the broad band of long wavelength transverse-optical modes appear from 580 to 400 nm(-1) for the clusters larger than 19 nm. 展开更多
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Semiempirical prediction of the hyperpolarizabilities for cyanovinyl-substituted donor-acceptor molecules
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作者 Zhao, CY Zhang, Y +1 位作者 Fang, WH You, XZ 《Chinese Journal of Chemistry》 SCIE CAS CSCD 1996年第5期393-398,共6页
We present here a systematically theoretical study on the nonlinearities and their structure-property relationship of cyanovinyl-substituted donor-acceptor molecules by virtue of semiempirical PM3/AM1-FF approach. Goo... We present here a systematically theoretical study on the nonlinearities and their structure-property relationship of cyanovinyl-substituted donor-acceptor molecules by virtue of semiempirical PM3/AM1-FF approach. Good consistency between measured and calculated hyperpolarizabilities is obtained. Results show that conformation has a significant effect on hyperpolarizabilities. The torsion angle change between two conjugated parts of the molecular systems can substantially alter the nonlinearities. The total amount of charge transfer difference from donor to acceptor has been introduced to understand the microscopic nature of the nonlinear optical properties for the title molecules. General guidelines may be sought out in the search of molecules with large values of beta. Some molecules with large molecular hyperpolarizabilities can be predicted by the optimization for the longer pi-electron systems with both acceptor and donor groups. 展开更多
关键词 nonlinear optics HYPERPOLARIZABILITIES PM3 method cyanovinyl-substituted molecules
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