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71.
Dipole moments and static dipole polarizabilities are calculated for neon and the molecules HF, H2O, NH3, CH4 and CO from SCF and correlated wavefunctions. The construction of appropriate gaussian-type basis sets is discussed and the convergence of the correlation contributions to the polarizability is analysed. The effect of vibrational averaging is also investigated. The polarizabilities as obtained from the coupled electron pair approximation (CEPA) with the most extended basis sets differ from experimental values by less than 1·5 per cent in all cases. The calculated polarizability anisotropies appear to be correct to about 5–15 per cent. The correlation contributions to the polarizabilities are found to vary from 3 to 12 per cent. 相似文献
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Dieter Seebach Jean-Marc Lapierre Wilfried Jaworek Paul Seiler 《Helvetica chimica acta》1993,76(1):459-475
The aldol adducts 1a – 13a of R,R-2(tertbutyl)-6-methyl-1,3-dioxan-4-one (from 3-hydroxybutanoic acid) to aldehydes, single diastereoisomers obtained as described previously, are acetylated or benzoylated to the corresponding esters 1b – 5b and 6c – 13c , respectively, which in turn are reduced with LiAlH4 to the title compounds 14 – 24 . The enantiomerically pure triols thus available may be useful as chiral building blocks, as auxiliaries for enantioselective reactions, and as center pieces for chiral dendrimers. 相似文献
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Klaus D. A. Wendt Klaus Blaum Christopher Geppert Peter Müller Wilfried Nörtershäuser Annette Schmitt Philipp Schumann Norbert Trautmann Bruce A. Bushaw 《Hyperfine Interactions》2005,162(1-4):147-157
A variety of research activities in the field of fundamental and applied nuclear physics has evolved in the last years using
resonantly tuned radiation from powerful lasers. The technique of resonance ionization spectroscopy has delivered outstanding
results and found broad acceptance in the last years as a particularly efficient and highly selective method for rare and
exotic radioisotope studies. It is used for production, spectroscopy and detection of these species and provides complete
isobaric, high isotopic and even some isomeric selection, which altogether is needed for on-line investigation of short lived
species far off stability as well as for ultra trace determination. Good overall efficiency pushes the experimental limits
of detection in elemental trace analysis down to below 106 atoms per sample, and additionally isotopic selectivity as high as 3 × 1012 has been demonstrated. The widespread potential of resonance ionization techniques is discussed, focusing on the experimental
arrangements for applications in selective on-line isotope production, spectroscopy of rare radioisotopes and ultra trace
determination of radiotoxic isotopes like 238Pu to 244Pu, 135,137Cs, 89,90Sr or 41Ca in environmental, technical and biomedical samples. 相似文献
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Wilfried Imrich J.M.S Simões-Pereira Christina M Zamfirescu 《Journal of Combinatorial Theory, Series B》1984,36(1):1-15
This paper extends previous results of the authors. In particular, non-treerealizable metrics are investigated and it is shown that every finite metric has an optimal realization by a graph. 相似文献