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101.
Amaral A. M. S. C. Linnett J. W. Williamson C. T. 《Theoretical chemistry accounts》1970,16(4):249-262
A full configuration interaction treatment has been carried out for the four electrons of the double bond of ethylene using a minimal STO basis set. The excent to which - separability provides a good approximation for the eigenfunctions of the low-lying states and for transitions between them has been examined. Alternative formulations using various more localised orbitals as the basis are derived for a number of the states. These have been examined and discussed.
We wish to thank the Instituto de Alta Cultura of Portugal for a scholarship for A. A. and the National Science Foundation (USA) for a post-doctoral fellowship for C.T.W. 相似文献
Zusammenfassung Eine vollständige Konfigurationswechselwirkung wurde für die vier Elektronen der Doppelbindung von Äthylen durchgeführt, wobei eine minimale STO-Basis benutzt wurde. Das Maß, in dem die --Separierbarkeit eine gute Näherung für Eigenfunktionen der niedrigliegenden Zustände und für Übergänge zwischen ihnen darstellt, wurde untersucht. Alternativformulierungen, die verschiedene, lokalisierte Orbitale als Basis benutzen, werden für eine Anzahl von Zuständen angegeben und diskutiert.
Résumé Interaction de configuration complète pour les quatre électrons de la double liaison de l'éthylène dans une base STO minimale. La séparabilité - est examinée pour les plus bas états et les transitions entre ces états. D'autres formulations utilisant des orbitales plus localisées sont obtenues pour certains états. Ces formulations sont discutées.
We wish to thank the Instituto de Alta Cultura of Portugal for a scholarship for A. A. and the National Science Foundation (USA) for a post-doctoral fellowship for C.T.W. 相似文献
102.
Kesson T Albrow MG Almehed S Benary O Boggild H Botner O Breuker H Brody H Burkert V Callen B Carter AA Carter JR Cecil P Choi Y Cleland WE Dam P Dagan S Dahl-Jensen E Dahl-Jensen I Damgaard G Evans WM Fabjan CW Frandsen P Frankel S Frati W Gordon H Goerlach U Hansen KH Hedberg V Hooper JE Jarlskog G Kessler G Killian T Kroeger R Kulka K v d Lans J Lissauer D Lörstad B Ludlam T McCubbin NA Möller R Molzon W Nielsen BS Olsen LH Oren Y Rosso E Rudge A Specht H Stumer I Thompson JA Thorstensen G 《Physical review letters》1985,55(23):2535-2538
103.
Gary E. Martin R. Thomas Williamson Peter G. Dormer Wolfgang Bermel 《Magnetic resonance in chemistry : MRC》2012,50(8):563-568
ADEQUATE experiments provide an alternative to the more commonly employed GHMBC experiment for the establishment of long‐range heteronuclear connectivities. The 1,1‐ADEQUATE experiment allows the unequivocal identification of both protonated and non‐protonated carbon resonances adjacent to a protonated carbon. The 1,n‐ADEQUATE experiment establishes correlations via an initial 1JCH heteronuclear transfer followed by an nJCC out‐and‐back transfer, most typically, via three carbon–carbon bonds. Hence, the 1,n‐ADEQUATE experiment allows the equivalent of 4JCH heteronuclear correlations to be probed when they are not observed in a GHMBC spectrum. Aside from the lower sensitivity of the 1,n‐ADEQUATE experiment relative to GHMBC experiments, the interpretation of the former is also complicated by the ‘leakage’ of 1JCC correlations into the spectrum that must be identified. A method for the inversion of 1JCC correlations to facilitate the interpretation of 1,n‐ADEQUATE spectra is presented that allows a single experiment to be performed to access 1JCC and nJCC correlation information. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
104.
David P. Williamson 《Operations Research Letters》2007,35(6):707-712
We present a very simple way of derandomizing the algorithm proposed by Gupta, Kumar and Roughgarden for single source rent-or-buy by using the method of conditional expectation. Using the improved analysis of Eisenbrand, Grandoni and Rothvoß, our derandomized algorithm has an approximation guarantee of 3.28. 相似文献
105.
The specific heat CP is found to vary as in the critical region above TN for the antiferromagnets GdSb and HoSb. This correspondence holds despite a dramatic difference between the two systems in the strength of the divergence CP = A??α, , where for HoSb we find α = 0.83 ± 0.10 while for GdSb α = 0.20 ± 0.10. 相似文献
106.
Coupled cluster calculations provide a one‐to‐one mapping between calculated and observed transition energies in the electronic absorption spectrum of zinc phthalocyanine 下载免费PDF全文
Andrew J. Wallace Bryce E. Williamson Deborah L. Crittenden 《International journal of quantum chemistry》2017,117(8)
All transitions in the experimentally designated and numbered Q, B, and N bands (< 4.8 eV) of the electronic absorption spectrum of zinc phthalocyanine (ZnPc) are assigned on the basis of one‐to‐one agreement between calculated and experimentally observed transition energies and oscillator strengths. Each band in this range of the spectrum represents a ligand‐based transition that originates from a combination of occupied orbitals and terminates in the lowest unoccupied molecular orbital (LUMO, ). Transition energies in the L and C regions (4.8–6.5 eV) are harder to capture quantitatively, due to the partial Rydberg character of some of the excited states, and so are tentatively assigned here. Most transitions in this range correspond to excitations from the HOMO or lower‐energy orbitals to π orbitals above the LUMO. 相似文献
107.
108.
William G. Proud David M. Williamson John E. Field Stephen M. Walley 《Chemistry Central journal》2015,9(1)
Abstract
Advances in experimental, high-speed techniques can be used to explore the processes occurring within energetic materials. This review describes techniques used to study a wide range of processes: hot-spot formation, ignition thresholds, deflagration, sensitivity and finally the detonation process. As this is a wide field the focus will be on small-scale experiments and quantitative studies. It is important that such studies are linked to predictive models, which inform the experimental design process. The stimuli range includes, thermal ignition, drop-weight, Hopkinson Bar and Plate Impact studies. Studies made with inert simulants are also included as these are important in differentiating between reactive response and purely mechanical behaviour.Graphical abstract
相似文献109.
Williamson LN Terry AV Bartlett MG 《Rapid communications in mass spectrometry : RCM》2006,20(18):2689-2695
A method has been developed to quantify chlorpyrifos (O,O-diethyl-O-[3,5,6,-trichloro-2-pyridyl] phosphorothionate) and its metabolites chlorpyrifos-oxon (O,O-diethyl-O-[3,5,6,trichloro-2-pyridinyl] phosphate) and TCP (3,5,6,-trichloro-2-pyridinol) in rat brain tissue by coupled-column liquid chromatography/electrospray ionization tandem mass spectrometry (LC/LC/ESI-MS/MS). Rat brains were homogenized and treated by protein precipitation using ice-cold acetonitrile. The supernatant was directly injected onto the coupled-column system. Sample clean-up was achieved on a Zorbax Extend-C(18) column (2.1 x 50 mm, 5 microm) using a mobile phase of acetonitrile/water with 0.0025% formic acid (40:60, v/v). The compounds were separated isocratically on a Zorbax Eclipse XDB C(8) column (2.0 x 150 mm, 5 microm) using a mobile phase of acetonitrile/water with 0.0025% formic acid (75:25, v/v). Chlorpyrifos and chlorpyrifos-oxon were detected in positive ion mode using multiple reaction monitoring (MRM). TCP was detected in negative ion mode using precursor-to-precursor transition monitoring. The method was validated and the specificity, linearity, limit of quantitation (LOQ), precision, accuracy, stability, and recoveries were determined. Calibration curves for all three analytes yielded correlation coefficients of 0.993 or greater. The LOQs were 25.3 ng/g for chlorpyrifos and 6.3 ng/g for chlorpyrifos-oxon and TCP. All precision relative standard deviations (RSDs) were less than 16% for the LOQ and less than 11% for the other QC samples. This method was successfully applied to six rats that were injected subcutaneously with chlorpyrifos. 相似文献
110.
Wenzel SC Williamson RM Grünanger C Xu J Gerth K Martinez RA Moss SJ Carroll BJ Grond S Unkefer CJ Müller R Floss HG 《Journal of the American Chemical Society》2006,128(44):14325-14336
Feeding experiments with isotope-labeled precursors rule out hydroxypyruvate and TCA cycle intermediates as the metabolic source of methoxymalonyl-ACP, the substrate for incorporation of "glycolate" units into ansamitocin P-3, soraphen A, and other antibiotics. They point to 1,3-bisphosphoglycerate as the source of the methoxymalonyl moiety and show that its C-1 gives rise to the thioester carbonyl group (and hence C-1 of the "glycolate" unit), and its C-3 becomes the free carboxyl group of methoxymalonyl-ACP, which is lost in the subsequent Claisen condensation on the type I modular polyketide synthases (PKS). d-[1,2-(13)C(2)]Glycerate is also incorporated specifically into the "glycolate" units of soraphen A, but not of ansamitocin P-3, suggesting differences in the ability of the producing organisms to activate glycerate. A biosynthetic pathway from 1,3-bisphosphoglycerate to methoxymalonyl-ACP is proposed. Two new syntheses of R- and S-[1,2-(13)C(2)]glycerol were developed as part of this work. 相似文献