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991.
The one-electron oxidized linear pentanuclear nickel complexes [Ni(5)(tpda)(4)(H(2)O)(BF(4))](BF(4))(2) (1) and [Ni(5)(tpda)(4)(SO(3)CF(3))(2)](SO(3)CF(3)) (2) have been synthesized by reacting the neutral compound [Ni(5)(tpda)(4)Cl(2)] with the corresponding silver salts. These compounds have been characterized by various spectroscopic techniques. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 15.3022(1) A, b = 31.0705(3) A, c = 15.8109(2) A, beta = 92.2425(4) degrees, V = 7511.49(13) A(3), Z = 4, and compound 2 crystallizes in the monoclinic space group C2/c with a = 42.1894(7) A, b = 17.0770(3) A, c = 21.2117(4) A, beta = 102.5688(8) degrees, V = 14916.1(5) A(3), Z = 8. X-ray structural studies reveal an unsymmetrical Ni(5) unit for both compounds 1 and 2. Compounds 1 and 2 show stronger Ni-Ni interactions as compared to those of the neutral compounds. 相似文献
992.
The adsorption isotherms of the binary mixtures of ethanol/n-Octane, ethanol/n-hexadecane and n-octane/n-hexadecane onto the activated carbon TA 95 were measured at 278 K, 288 K, 298 K and 308 K and described with mathematical functions. About 300 experimental values of the adsorption excess of the ternary mixture ethanol/n-octane/n-hexadecane onto activated carbon TA 95 at 298 K were measured by gas chromatography inside the ternary triangle. The ternary miscibility gap was determined at three temperatures. A good representation of the ternary data and the calculated activity coefficients (using the UNIFAC model) in three-dimensional space was possible with the help of transformation of coordinates. It was possible, too, by utilization of the conception of the quasi two-component representation of the mole fractions with and without miscibility gap. Several influencing factors on ternary adsorption isotherms were discussed for the system ethanol/n-octane/n-hexadecane/TA 95. 相似文献
993.
We synthesized dialkoxy-substituted poly[phenylene vinylene]s (dROPPV-1/1, 0.2/1, and 0/1) consisting of two repeating units with different side-chain lengths (methoxy and 3,7-dimethyloctyloxy). These polymers can serve as a model system to clarify roles of aggregates (the sites with ground-state interchain interactions) and the independent chain segments in the well-packed chains (the chain segments that are compactly packed without interaction) in the emission mechanism of conjugated polymers. Due to the packing of polymer chains, films of all of these polymers are accessible to interchain excitations, after which excitons can re-form to result in delayed luminescence. Besides, some chains form aggregates so that the delayed luminescence is no more the ordinary single-chain emission but red-shifted and less structured. Not only the re-formation of these indirect excitons but also the aggregation of chains are facilitated in the polymers with short methoxy side groups, revealing that both packing and aggregation of chain segments require a short spacing between polymer chains. However, the incorporation of other side chains such as the 3,7-dimethyloctyloxy group to dROPPVs is necessary for the formation of aggregates because these long branched side chains can reduce the intrachain order imposed by the short methoxy groups, which accounts for the absence of aggregate emission in the well-studied poly[2,5-dimethoxy-1,4-phenylene vinylene]. This study reveals that the well-packed chains do not necessarily form aggregates. We also show that the photophysical properties and the film morphology of conjugated polymers can be deliberately controlled by fine-tuning of the copolymer compositions, without altering the optical properties of single polymer chains (e.g., as in dilute solutions). 相似文献
994.
995.
Equilibrium geometries for the electronic ground and first excited singlet states of 1,1'-binaphthyl have been calculated by minimization of the total energy with respect to all internal coordinates. Using these results, an interpretation of the fluorescence S1→ S0 and absorption spectra Sm ← S0 and Sn ← S1 in rigid and fluid solutions is given.For the first time the equilibrium geometry of the first excited singlet state of 1, 1′-binaphthyl has been calculated. On excitation to the S1 state the dihedral angle θ between the two naphthalene moieties is de- creased from 61 ° to 41 °. A detailed survey of CH bond lengths in the S0 and S1 states has been given. This result should be of particular importance for the theoretical treatment of radiationless transitions.Using equilibrium geometries for the S0 and S1 states a satisfactory interpretation of the Sm ← S0 and Sn ← S1 absorption spectra as well as of the fluorescence spectra in fluid and rigid solutions can be given. Concerning the Sn ← S1 absorption spectrum in fluid solution, the calculations predict a strong absorption (A ← B transition) in the still uninvestigated region of energies lower than 11000 cm?1.From the results of this paper and of other calculations it can be concluded that the Warshel-Karplus method yields reliable equilibrium geometries for electronic ground and excited states of unsaturated hydrocarbons [22,23]. 相似文献
996.
In this article methods are presented for the separation and identification of unusual cis, cis dienoic and polygnoic long chain fatty acids. Special emphasis has been laid on the identification of cis, cis octadecadienoic acids. The steps followed are: after transesterification the fatty acid methyl esters are separated by preparative gas chromatography according to chain length followed by argentation chromatography on thin-layer plates. After hydroxylation of the double bonds with osmium tetroxide the polyhydroxy compounds are derivatized to the per-O-trimethylsilyl-ethers. Separation and identification of individual compounds are achieved by combined gas chromatography-mass spectrometry using SCOT columns and low ionization energy. 相似文献
997.
On Hexagonal Perovskites with Cationic Vacancies. XVII. Structure Determination on Ba9Nb6W□2O27 – the First Stacking Polytype of a Rhombohedral 27 L-Type The hexagonal stacking polytype of rhombohedral 27 L -type, Ba9Nb6W□2O27, crystallizes in the space group R3 m with the sequence (4)1(3)1 ? (hhccchhcc)3 and three formula units for the trigonal setting. The refined, intensity related, R'-value is 9.7percnt;. The octahedral net consists of blocks of three face connected octahedra which are linked to each other alternately through one or two octahedra connected exclusively by common vertices. The cationic vacancies are located in the centers of the groups of three octahedra. With this distribution direct contact between occupied face-sharing octahedra is avoided. The niobium and tungsten atoms are distributed statistically between the remaining octahedral holes. In the blocks of three octahedra they are displaced by ≈ 0.29 Å from their ideal positions in the direction of the central void. The Ba atoms neighbouring a vacancy (all in hexagonal packed BaO3 sheets) are dislocated in the direction of the void, while the cubic packed BaO3 sheets maintain nearly regular form. 相似文献
998.
A theoretical model for the multiline TEA CO2 laser has been developed which takes into account the overlap of the P(20) line of (0001) (1000) regular band transition with the R(23) line of (0111) (1110) hot band transition. The model is used for the study of the influence of different parameters like laser gas temperature, gas mixture and pump rates on laser intensities of different rotational lines. This study explains the experimental results of the high power multiline TEA CO2 laser very well. 相似文献
999.
Dr. J. Dembczyński W. Ertmer U. Johann P. Stinner 《Zeitschrift für Physik A Hadrons and Nuclei》1980,294(4):313-317
The hyperfine structure of the metastable atomic states (3d 74s)5 F 2,3,4,5 and (3d 7 4s)3 F 2,3,4 of57Fe has been measured using theABMR- LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence). From these measurements the following hfs constantsA of the magnetic dipole interaction have been obtained (corrected for second order effects):A(5 F 2)=55.994(7) MHzA(5 F 3)=69.632(5) MHzA(5 F 4)=78.435(4) MHzA(5 F 5)=87.246(3) MHzA(3 F 2)=143.328(4) MHzA(3 F 3)=50.602(10) MHzA(3 F 4)=13.456(5) MHz 相似文献
1000.
Our study of Anderson's tight binding model for strongly disordered electronic systems is extended to a numerical treatment of thed c-conductivity atT=0. For 100 × 100 square lattices, 129 × 129 triangular lattices, and for diamond lattices with 27,000 sites, the behaviour of is studied as a function of the Fermi energy and the disorder. The calculations are based on the exact eigenfunction representation of the Kubo formula, which is evaluated by the systematic application of recursion algorithms. Our results are in favour of Mott's original suggestion of a minimum metallic conductivity
min, both in two and three dimensions. In two dimensions we find the universal value of
min=(0.11 ±0.02)e
2/.
Based on the thesis of J. Stein, Regensburg 1979 相似文献