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131.
H. J. Wollersheim P. Egelhof H. Emling J. Gerl W. Henning R. Holzmann R. Schmidt R. S. Simon N. Martin G. Eckert Th. W. Elze K. Stelzer R. Kulessa G. Duchene B. Haas J. C. Merdinger J. P. Vivien J. de Boer E. Hauber K. Kaiser P. von Brentano R. Reinhardt R. Wirowski R. Julin C. Fahlander I. Thorslund H. Kluge 《Zeitschrift für Physik A Hadrons and Nuclei》1992,341(2):137-144
Collective properties of206,208Pb have been investigated with gamma-ray spectroscopy using nuclear and electromagnetic excitation by208Pb projectiles. From the measurement of particle-particle- and particle-particle- coincidences a new energy level in208Pb at 5.683 MeV was observed and the data suggest an interpretation as a 2-phonon octupole vibrational state with spin 4+ or 6+. For this state one finds the same dynamical deformation parameter
3 as for the first-excited collective 3– state. The results are compared to predictions of models which consider, in particular, the aspects of the quadrupole interaction and the interaction of the 2-particle pairing vibration with the 2-phonon octupole vibration. For the206Pb+208Pb system at 6.2 MeV/u the nuclear potential could be determined from the measured inelastic cross sections.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday 相似文献
132.
133.
The spatial structure of gels of sodium carboxymethyl cellulose (NaCMC-gel) and carboxymethyl cellulose in the free acid form can be imaged in the transmission electron microscope (TEM). The freeze-fracturing technique is suitable for this. Experiments with test preparations (10 % aqueous glycerol solution) show that cooling rates during freeze-fixing are decisive for visualization, and that cooling rates can be improved substantially by using a cryojet. The increase of the cooling rate to more than 15 000 K/s makes it possible to obtain extremely fine network structures with a mesh width of 5–25 nm and with a filament thickness of 2–3 nm. The results obtained after jet-freezing show differences in the structure of the two gels: quasi-crystalline microaggregates in the HCMC-gel can be seen, and they cause an increased elasticity and opalescence of the aged HCMC-gels. 相似文献
134.
The synthesis, structure, and reactivity of a series of low-coordinate Fe(II) diketiminate amido complexes are presented. Complexes L(R)FeNHAr (R = methyl, tert-butyl; Ar = para-tolyl, 2,6-xylyl, and 2,6-diisopropylphenyl) bind Lewis bases to give trigonal pyramidal and trigonal bipyramidal adducts. In the adducts, crystallographic and (1)H NMR evidence supports the existence of agostic interactions in solid and solution states. Complexes L(R)FeNHAr may be oxidized using AgOTf, and the products L(R)Fe(NHAr)(OTf) are characterized with (19)F NMR spectroscopy, UV/vis spectrophotometry, solution magnetic measurements, elemental analysis, and, in one case, X-ray crystallography. In the structures of the iron(III) complexes L(R)Fe(NHAr)(OTf) and L(R)Fe(OtBu)(OTf), the angles at nitrogen and oxygen result from steric effects and not pi-bonding. The reactions of the amido group of L(R)FeNHAr with weak acids (HCCPh and HOtBu) are consistent with a basic nitrogen atom, because the amido group is protonated by terminal alkynes and alcohols to give free H(2)NAr and three-coordinate acetylide and alkoxide complexes. The trends in complex stability give insight into the relative strength of bonds from three-coordinate iron to anionic C-, N-, and O-donor ligands. 相似文献
135.
Fan M Shevchenko IV Voorhies RH Eckert SF Zhang H Lattman M 《Inorganic chemistry》2000,39(21):4704-4712
Treatment of calix[4]arene (1b) with trichloromethylsilane yields two conformers of calix[4]SiMe(OH), the cone 2b-C and the partial cone 2b-PC. These are isolated and structurally characterized, and their thermodynamic activation parameters are determined in solution [Ea = 117(3) kJ/mol, delta H = 5(4) kJ/mol]. Similar parameters are found for the p-tert-butylcalix[4]arene analogues 2a-C and 2a-PC. Deprotonation of 2b with butyllithium yields calix[4]SiMe(OLi) (8b). The structure of 8b is solvent dependent: 8b contains a five-coordinate silicon in THF and a four-coordinate silicon in benzene. Similar behavior is found for the p-tert-butylcalix[4]arene analogues. The five-coordinate phosphorus analogue of the anion in 8, p-tert-butylcalix[4]PMe (11a), is synthesized from the phosphonium triflate salt p-tert-butylcalix[4]PMe(OH)OTf (10a(OTf)) via treatment with butyllithium. The structure of 11a shows the geometry around phosphorus to be very close to a pure trigonal bipyramid. The X-ray structure of 10a(OTf) cannot be obtained, but its iodide analogue 10a(T) is synthesized and structurally characterized. The cation in 10a(I) adopts the partial cone conformation in the solid state, similar to 2b-PC. Treatment of 8b with methyl trifluoromethanesulfonate yields the methyl phenyl ether calix[4]SiMe(OMe) (3b). This species and its p-tert-butyl analogue 3a are structurally characterized. Both adopt the partial cone conformation. The SiMe group in 3b can be removed via treatment with fluoride to yield the monomethylated calix[4]arene 4b in 50-60% overall yield based on 1b. 相似文献
136.
Campidelli S Deschenaux R Eckert JF Guillon D Nierengarten JF 《Chemical communications (Cambridge, England)》2002,(6):656-657
Functionalization of C60-oligophenylenevinylene derivatives with a cyanobiphenyl-terminated dendromesogen leads to new donor-acceptor systems with liquid-crystalline properties. 相似文献
137.
138.
Isotopic-yield ratios of complex fragments from intermediate-energy heavy-ion reactions 总被引:1,自引:0,他引:1
139.
140.
Nierengarten JF Eckert JF Rio Y Carreon MP Gallani JL Guillon D 《Journal of the American Chemical Society》2001,123(40):9743-9748
A new dendron with peripheral long alkyl chains and containing five C(60) units in the branching shell has been prepared and attached to a Fréchet-type dendron functionalized with ethylene glycol chains. The peripheral substitution of the resulting globular dendrimer with hydrophobic chains on one hemisphere and hydrophilic groups on the other provides the perfect hydrophobic/hydrophilic balance allowing the formation of stable Langmuir films. Furthermore, a perfect reversibility has been observed in successive compression/decompression cycles. The diblock structure of the dendrimer has been also crucial for the efficient transfer of the Langmuir films in order to obtain well-ordered multilayered Langmuir-Blodgett films. This approach appears particularly interesting since functional groups not well adapted for the preparation of Langmuir and Langmuir-Blodgett films such as fullerenes can be attached into the branching shell of the dendritic structure and, thus, efficiently incorporated in thin ordered films. 相似文献