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41.
Polycyclopentanes as Steroid Analoga The synthesis of linearly annellated pentaquinanes from a readily available triquinane is reported. 相似文献
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We use a multimode rate-equation model to investigate the stability of a laser system with second-order nonlinearity and compare the results with the literature on intracavity frequency-doubled lasers. The emphasis is on the Hopf bifurcation between the asymptotically stable state and the stable oscillation that occurs with variation of the conversion efficiency from the fundamental frequencies to their sum. This bifurcation results in two simple expressions that describe the stability curve, depending on material and cavity parameters. We also report on an experimental confirmation of the predicted temporal behavior of sum-frequency generation. 相似文献
44.
Daniel Hirschi Wolfgang Luef Peter Gerber Reinhart Keese 《Helvetica chimica acta》1992,75(6):1897-1908
The preparation and the X-ray structure analysis of cis, trans, cis, cis-10-hydroxy-[4.5.5.5]fenestrane-1-methanol ( 8b ) is reported. The measured bond angles and bond lengths of the central C(C)4 fragment are better reproduced by calculations with the AM 1 than by the MNDO method. 相似文献
45.
Fliegl H Köhn A Hättig C Ahlrichs R 《Journal of the American Chemical Society》2003,125(32):9821-9827
We report accurate geometries and harmonic force fields for trans- and cis-azobenzene determined by second-order M?ller-Plesset perturbation theory. For the trans isomer, the planar structure with C(2h) symmetry, found in a recent gas electron diffraction experiment, is verified. The calculated vibrational spectra are compared with experimental data and density functional calculations. Important vibrational frequencies are localized and discussed. For both isomers, we report UV spectra calculated using the second-order approximate coupled-cluster singles-and-doubles model CC2 with accurate basis sets. Vertical excitation energies and oscillator strengths have been determined for the lowest singlet n(pi)* and (pi)(pi)* transitions. The results are compared with the available experimental data and second-order polarization propagator (SOPPA) and density functional (DFT) calculations. For both isomers, the CC2 results for the excitation energies into the S(1) and S(2) states agree within 0.1 eV with experimental gas-phase measurements. 相似文献
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48.
The cyclododecadiynes 3b–d, 8b–d , and 10b–c with functionalities in two propargylic positions, as well as the monofunctionalized diyne 13b have been prepared from simple open-chain building blocks. In the DMPU ( = N,N'-dimethylpropyleneurea)-assisted ring-closing alkylation of 1,7-diynes, the twelve-membered ring compounds have been prepared in yields of 16–55%. The preparation of the diene-diyne 15 and the cyclododeca-5,11-diyne-1,4-dione 18 are described. 相似文献
49.
Karin Eichkorn Florian Weigend Oliver Treutler Reinhart Ahlrichs 《Theoretical chemistry accounts》1997,97(1-4):119-124
We present auxilliary basis sets for the atoms H to At – excluding the Lanthanides – optimized for an efficient treatment
of molecular electronic Coulomb interactions. For atoms beyond Kr our approach is based on effective core potentials to describe
core electrons. The approximate representation of the electron density in terms of the auxilliary basis has virtually no effect
on computed structures and affects the energy by less than 10−4 a.u. per atom. Efficiency is demonstrated in applications for molecules with up to 300 atoms and 2500 basis functions.
Received: 17 December 1996 / Accepted: 8 May 1997 相似文献
50.
M. D. Blue P. B. Reinhart J. J. Gallagher 《International Journal of Infrared and Millimeter Waves》1980,1(2):255-261
The techniques of coherent transient spectroscopy have been successfully applied to the microwave and optical regions of the spectrum, but lack of suitable sources has prevented convenient extension to the millimeter/submillimeter region where several strong molecular transitions occur. Analysis of the experimental requirements and theory for such experiments considering several molecules including H2O and CH3Cl indicates how such experiments can be performed employing recently developed oscillators with increased power. 相似文献