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981.
Colourless needles of mercurous dimethylglyoximato nitrate, Hg2(Dmg)2(NO3)2, grow from a diluted nitric acid solution of mercurous nitrate and dimethylglyoxime. The crystal structure (triclinic, P1¯, a = 728.50(13), b = 1066.8(2), c = 1167.9(2) pm, α = 93.78(2)°, β = 94.16(2)°, γ = 98.61(2)°, Rall = 0, 0726) contains the cations [Hg2(Dmg)2]2+ and “non‐coordinating” (NO3)— anions. In the cation, two neutral dimethylglyoxime molecules coordinate bidentately with Hg—N distances in the narrow range of 236 to 239 pm to the mercurous ion, Hg22+, which exhibits a Hg—Hg bond distance of 252.23(8) pm). 相似文献
982.
G. Vanden Berghe H. De Meyer M. Van Daele 《International Journal of Theoretical Physics》1995,34(9):1931-1937
An infinite set of exact solutions for the three-dimensional Schrödinger equation with the interactionsar 2+br4+cr6 andr 2+λr2/(1+gr 2) is presented. The conditions under which these solutions can occur are given. Some previously published errors are corrected. 相似文献
983.
Results of quantum and semiclassical calculations obtained for two different potential-energy surfaces are used to discuss spectroscopic properties and isotope effects of the linear IHI and IDI molecules. The potentials are a purely repulsive LEPS surface and a DIM-3C potential with two van der Waals type minima for equivalent IH ··· I and I ··· HI configurations. Both systems are dominated by the effect of vibrational bonding giving rise to some very unusual spectroscopic phenomena, which are discussed in detail. The different vibrational frequencies and rotational constants are roughly estimated as ν1 = 120 (100) cm?1, ν2 = 280 (210) cm?1, ν3 = 360 (160) cm?1 and B = 0.0194 (0.0196) cm?1 for IHI (IDI). A detailed discussion of the dependence of ν1, ν2 and B on ν3, their sensitivity to variations of the potential-energy surface, and a comparison with the vibrational frequencies of I2 and HI (ID) is given. It is predicted that there exists only one excited level of the antisymmetric stretching mode. The numbers of symmetrical stretching and bending levels are fairly constant or may even decrease upon deuteration. Simultaneously deuteration destabilizes the molecule. These unusual phenomena are rationalized by our calculations. A set of criteria for observing infrared and Raman bound-to-bound and bound-to-resonance state transitions are presented for the IHI and IDI molecule. 相似文献
984.
Ohne Zusammenfassung 相似文献
985.
We have measured the rheological properties of two cholesterol derivatives (cholesteryl myristate and cholesteryl nonanoate) in the vicinity of their cholesteric-smecticA transitions. The results for the two compounds differ qualitatively, and are in agreement with results based on optical observations of new defects in cholesteryl nonanoate showing that this material, traditionally considered as a typical cholesteric, in fact exhibits a TGBA phase between the cholesteric and smectic A phases. 相似文献
986.
Thomas Meyer Pierre -A. Nicati Philippe A. Robert Dimitris Varelas Hans -G. Limberger René P. Salathé 《Optical Review》1997,4(1):A53-A55
This paper presents a new method for writing and erasing a birefringence in optical fibers by polarized ultra violet side-exposure.
This experiment gives new insight into the origin of the induced birefringence and some applications are outlined. 相似文献
987.
Periodica Mathematica Hungarica - 相似文献
988.
The liquid crystal behaviour of a family of non-symmetric liquid crystalline dimers is reported. These systems contain two bibenzoate rigid units that are linked to distinct terminal groups at one end, and to a flexible interconnecting spacer at the other. Several systems having different terminal and central chains are studied using calorimetric, microscopic and diffraction techniques. All the samples form phases with variable degrees of order (from low ordered smectic to crystalline phases) depending on the chemical constitution of the different segments. The influence of the length, parity and lateral substitution of the spacers on the transitional properties and the symmetry of the mesophases that are formed is analysed. It is found that a decrease in the transition temperatures and enthalpies occurs when the length of the flexible spacers increases, when lateral methyl substituents are introduced, or when the parity of the central spacer changes from an even to odd number of carbon atoms or ether groups. The arrangement of the mesogens and dissimilar flexible groups within the ordered structure is discussed with respect to the observed L/d ratios. Different values were obtained depending on the parity of the central spacer and on the degree of order. Interpenetrated structures, in which the flexible groups of different lengths are mixed, seem to be compatible with low ordered smectic phases, but sterically disfavoured when constructing crystalline phases. 相似文献
989.
990.
Hans Meyer 《Monatshefte für Chemie / Chemical Monthly》1894,15(1):164-182
Ohne Zusammenfassung 相似文献