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181.
Jeffrey R. Lancaster Rachael Smilowitz Nicholas J. Turro Jeffrey T. Koberstein 《Photochemistry and photobiology》2014,90(2):394-401
Small molecules representing common synthetic polymers were subjected to photochemically induced hydrogen abstraction by benzophenone. Reactions were monitored using 1H NMR to query the factors that influence preferential abstraction of protons in unique chemical environments. Differences in bond dissociation energies do not fully explain the observed hydrogen abstraction preferences. To that end, we identify contributions to abstraction from prereactive complexation, radical stability, steric effects and charge transfer effects. Using representative small molecule model compounds in lieu of polymeric materials is a novel approach to understanding photochemical reaction in polymers; however, it cannot probe the contributions of macromolecular effects—e.g. polymer rigidity or side chain and backbone mobility—to preferential hydrogen abstraction. 相似文献
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This paper is concerned with the development of a ‘best’ rank one transitive approximation to a general paired comparison matrix in a least‐squares sense. A direct attack on the non‐linear problem is frequently replaced by a sub‐optimal linear problem and, here, the best procedure of this kind is obtained. The Newton–Kantorovich method for the solution of the non‐linear problem is also studied, including the role of the best linear approximation as a starting point for this method. Numerical examples are included. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
186.
A Nonheme Sulfur‐Ligated {FeNO}6 Complex and Comparison with Redox‐Interconvertible {FeNO}7 and {FeNO}8 Analogues
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Aniruddha Dey Alex M. Confer Avery C. Vilbert Prof. Pierre Moënne‐Loccoz Prof. Kyle M. Lancaster Prof. David P. Goldberg 《Angewandte Chemie (International ed. in English)》2018,57(41):13465-13469
A nonheme {FeNO}6 complex, [Fe(NO)(N3PyS)]2+, was synthesized by reversible, one‐electron oxidation of an {FeNO}7 analogue. This complex completes the first known series of sulfur‐ligated {FeNO}6–8 complexes. All three {FeNO}6–8 complexes are readily interconverted by one‐electron oxidation/reduction. A comparison of spectroscopic data (UV/Vis, NMR, IR, Mössbauer, X‐ray absorption) provides a complete picture of the electronic and structural changes that occur upon {FeNO}6–{FeNO}8 interconversion. Dissociation of NO from the new {FeNO}6 complex is shown to be controlled by solvent, temperature, and photolysis, which is rare for a sulfur‐ligated {FeNO}6 species. 相似文献
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Yoshida S Reinhold CO Burgdörfer J Zhao W Mestayer JJ Lancaster JC Dunning FB 《Physical review letters》2007,98(20):203004
We report the first observation of echoes in the electric dipole moment of an ensemble of Rydberg atoms precessing in an external electric field F. Rapid reversal of the field direction is shown to play a role similar to that of a pi pulse in NMR in rephasing a dephased ensemble of electric dipoles resulting in the buildup of an echo. The mechanisms responsible for this are discussed with the aid of classical trajectory Monte Carlo simulations. 相似文献
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Lancaster KL Green JS Hey DS Akli KU Davies JR Clarke RJ Freeman RR Habara H Key MH Kodama R Krushelnick K Murphy CD Nakatsutsumi M Simpson P Stephens R Stoeckl C Yabuuchi T Zepf M Norreys PA 《Physical review letters》2007,98(12):125002
Kalpha x-ray emission, extreme ultraviolet emission, and plasma imaging techniques have been used to diagnose energy transport patterns in copper foils ranging in thickness from 5 to 75 microm for intensities up to 5x10(20) W cm-2. The Kalpha emission and shadowgrams both indicate a larger divergence angle than that reported in the literature at lower intensities [R. Stephens, Phys. Rev. E 69, 066414 (2004)]. Foils 5 microm thick show triple-humped plasma expansion patterns at the back and front surfaces. Hybrid code modeling shows that this can be attributed to an increase in the mean energy of the fast electrons emitted at large radii, which only have sufficient energy to form a plasma in such thin targets. 相似文献
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