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91.
Wolfgang K. Schubert J.F. Southern Lothar Schäfer 《Journal of Molecular Structure》1973,16(3):403-415
The structure of cis-1,4-ditertiarybutylcyclohexane(DTBC) was investigated by combined electron diffraction, conformational and vibrational analyses in order to obtain results which are more conclusive than those previously obtained by electron diffraction alone. In this study, first the minimum energy conformations for DTBC were calculated by the Westheimer-Hendrickson procedure using various force fields described in the literature; the same fields and the minimum energy conformations were used in subsequent vibrational analyses to calculate the mean amplitudes of vibration for each minimum energy conformation of DTBC; these mean amplitudes and the corresponding internuclear distances were then used to calculate the theoretical electron diffraction radial distribution curves which were compared to the experimental curves. The results indicate that the conformational energies of all the minimum energy chair and non-chair forms of DTBC are very similar. In excellent agreement with this, the theoretical radial distribution curves of all minimum energy forms have to be mixed for a best fit to the experimental radial distribution curve. A least squares analysis of the mixture under the described conditions yields for 110 °C a composition of approximately one third chair and two thirds non-chair forms. The quality of the empirical conformational force fields has a definite influence on the reliability of these results. 相似文献
92.
Doz. Dr. Friedrich Höfler Ernst Brandstätter 《Monatshefte für Chemie / Chemical Monthly》1975,106(4):893-904
The reactions of Ge2(C6H5)6 with HCl and HBr lead in nearly quantitative yields to the 1,1,2,2-tetrahalo derivatives Cl2(C6H5)GeGe(C6H5)Cl2 (I) and Br2(C6H5)GeGe(C6H5)Br2 (II), resp. The Si?Ge bond of (C6H5)3SiGe(C6H5)3 is cleaved under the conditions of hydrohalogenation. The vibrational spectra of Ge2Br6, Ge2(C6H5)6, I, and II are reported. The influence of vibrational coupling on ν GeGe in these compounds is discussed in detail, including vibrational calculations. 相似文献
93.
Zusammenfassung Es seiG eine endliche Untergruppe der orthogonalen Gruppe (det=±1) des
k
mitk=2 oder 3 undN eine endliche Menge von Punkten des
k
, welche unterG invariant ist. Dies gibt Anlass zu einer Permutationsdarstellung vonG im Vektorraum der komplexen Funktionen aufN.In Abschn. 3 wird für eine symmetriegerechte Basis angegeben. Dabei sind die Funktionswerte jeweils exakt tabelliert.
Im Buch [1] wurden lediglich die Diedergruppen behandelt (in Abschn. 3.1). 相似文献
Let G be a finite subgroup of the orthogonal group (det=±1) of k wherek=2 or 3 and letN be a finite set of points of k , which is invariant underG. In this way one gets a permutation representation ofG in the vector space of the complex functions onN.In Section 3, a symmetry adapted basis is given for , where the function values are tabulated exactly.
Im Buch [1] wurden lediglich die Diedergruppen behandelt (in Abschn. 3.1). 相似文献
94.
L. Käubier H. Prade F. Dönau U. Hagemann F. Stary K. -G. Rensfelt 《Zeitschrift für Physik A Hadrons and Nuclei》1981,299(3):251-261
The magnetic moments of the 5/2 1 + state in117Te at 274.4 keV and of the 7/2 1 + state in121Te at 443.1 keV have been determined asμ exp(5/2+)=?0.75(5)n.m. andμ exp(7/2+)=+0.63(7) n.m., respectively, using the TDPAD method and the reactions115,119Sn(α,2n)117,121Te. An evaluation method is described which provides, in case of the normalized time differential patternR(t) exhibits less than half of an oscillation period, a unique value of the Larmor frequency. The comparison of the measured magnetic moments with Nilsson-, soft rotor Coriolis- as well as core-particle coupling calculations gives valuable hints on the shape dependence of magnetic moments and, consequently, on the deformation of different states in the odd transitional nuclei117–125Te. In the light of the core-particle coupling model the positive parity states of117Te and121Te are interpreted as the members ofΔJ=1 andΔJ=2 bands built on thes 1/2,d 3/2,d 5/2 and g7/2 single-particle states, respectively. 相似文献
95.
J. Kolehmainen H. Häkkinen M. Manninen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,40(1):306-309
The shapes of metal clusters (with 2 to 14 valence electrons) on an inert surface are studied with a simple model based on the ultimate jellium model. It is shown that within certain approximations the surface-cluster interaction can be described with an external potential in the Kohn-Sham method. No restrictions for the cluster geometry are imposed. The results show that depending on the strength of the interaction and on the size of the cluster, the ground state is either planar or three-dimensional, but in many cases both geometries are stable and there is a marked energy barrier between them. The results agree qualitatively with ab initio calculations of Na clusters on a NaCl(100) surface. 相似文献
96.
B. Wierczinski J. Alstad K. Eberhardt J. V. Kratz R. Malmbeck M. Mendel A. Nähler J. P. Omtvedt G. Skarnemark N. Trautmann N. Wiehl 《Journal of Radioanalytical and Nuclear Chemistry》1998,238(1-2):193-197
The nucleus23Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution
and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the24Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an
exact energy calibration within 7 MeV,56Fe(n,γ)57Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the27Al(p,γ)28Si reaction atE
p=2046 keV. The neutron binding energy of24Na was determined to be 6959.75 keV. 相似文献
97.
R. Wäppling L. Häggström T. Ericsson S. Devanarayanan E. Karlsson B. Carlsson S. Rundqvist 《Journal of solid state chemistry》1975,13(3):258-271
The para- to ferromagnetic transition in Fe2P has been studied using Mössbauer spectroscopy. The magnetic hyperfine fields drop abruptly from about half of their saturation values to zero at 214.5 K indicating a first order transition. The isomer shifts show a discontinuous change at the transition point. For some samples the transition takes place over a wide temperature range, probably due to impurities and other imperfections in the samples. From the magnetic hyperfine fields at 15 K the magnetic moments can be deduced to be 1.14 μB and 1.78 μB for Fe(1) and Fe(2), respectively. An assignment of the components in the Mössbauer spectra to the two crystallographically nonequivalent iron positions has been made from the temperature variation of the spectra.The ordering of metal vacancies has been investigated by a Mössbauer study of a nonstoichiometric Fe2P sample and by an X-ray diffraction study of a nonstoichiometric Mn2P crystal. 相似文献
98.
The intensity dependence of photocurrent transients excited by the 1.06 μ line of a Nd laser has been measured. Observation of an I2 and an I3 branch indicate that charge carriers can be generated via two-quantum absorption and that at high intensities photoionization of a neutral excited state with a lifetime of the order 10?10 s dominates. 相似文献
99.
Thermodynamic quantities of a polyelectroyte immersed in salt solution are derived modeling the polyelectrolyte by a sequence of charged parallel flat plates. The starting point for the analysis is the derivation of the Gibbs free enthalpy in its canonic variables pressure (p) and temperature (T), i.e., as a thermodynamic potential. From this, further thermodynamic quantities such as Helmoltz free energy, entropy, internal energy, compressibility, isobar and isochor heat capacities, and expansive force are derived in analytical expressions by differentiation. All these formulas contain the parameter plate surface charge density (sigma) that provides a measure of the discontinuity of the polymer charge distribution that can be used to fit the theory to experimental data. Thermodynamic quantities are also known from the classical Donnan equilibrium that treats the polyelectroyte charge network as a charge continuum. A limiting process is used to perform the transition from the laminar Poisson- Boltzmann model to the continuous Donnan equilibrium. In general, the expressions of the Donnan system are recovered for plate charge density sigma-->0, number of plates Z-->infinity, and sigma Z=constant. Copyright 2000 Academic Press. 相似文献
100.
The synthesis and the photochemical behaviour of 4 new 2H-1.4-oxazines and 3 new spiro-2H-1.4-oxazines is described. 相似文献