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51.
An unambiguous method for distinguishing between abstraction-addition and addition-abstraction mechanisms (and mixtures thereof) in the reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl with a specifically deuterated cyclohexene, 1,2-dideuteriocyclohexene, is demonstrated. 相似文献
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Thermolysis of 4-aminophenyl benzyl sulfide at 523 K in the hydrogen donor solvent (HDS), 9,10-dihydroanthracene (AnH2), gave 4-aminothiophenol and toluene as the predominant products of the homolytic S-C bond cleavage. Under these conditions, a portion of the 4-aminothiophenol was desulfurized to aniline with first-order kinetics and with a rate constant estimated by kinetic modeling to be 7.0x10(-6) s-1. Starting with 4-NH2C6H4SH at 523 K, it was found that sulfur loss was more efficient in the non-HDSs, anthracene and hexadecane, than in AnH2. Under similar (competitive) reaction conditions, YC6H4SHs with Y=H, 4-CN, and 3-CF3 were completely inert; with Y=4-CH3O, there was some very minor desulfurization, whereas with Y=4-N(CH3)2 and 4-N(CH3)(H), the sulfur extrusions were as fast as that for Y=4-NH2. We tentatively suggest that this apparently novel reaction is a chain process initiated by the bimolecular formation of diatomic sulfur, S2, followed by a reversible addition of ground state, triplet 3S2 to the thiol sulfur atom, 4-NH2C6H4S upward arrow(SS upward arrow)H, and insertion into the S-H bond, 4-NH2C6H4SSSH. In a cascade of reactions, aniline and S8 are formed with the chains being terminated by reaction of 4-NH2C6H4S upward arrow(SS upward arrow)H with 4-NH2C6H4SH. Such a reaction mechanism is consistent with the first-order kinetics. That this reaction is primarily observed with 4-YC6H4SH having Y=N(CH3)2, N(CH3)(H), and NH2 is attributed to the fact that these compounds can exist as zwitterions. 相似文献
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古新安 朱韦臻 罗志伟 ANDREEV Y M LANSKII G V SHAIDUKO A V IZAAK T I SVETLICHNYI V A VAYTULEVICH E A ZUEV V V 《中国光学与应用光学文摘》2011,(6)
采用水平区熔法生长了碲(Te)掺杂浓度(质量百分比)分别为0.05%,0.1%,0.5%,1%,2%的硒化镓(GaSe)晶体,并分别对掺杂浓度为0.01%,0.07%,0.38%,0.67%,2.07%的GaSe∶Te晶体的光学性能进行了表征。首次研究了GaSe∶Te晶体中刚性层声子模式的转换。吸收光谱测试结果表明:当Te掺杂浓度小于0.38%时,振动中心位于0.59 THz附近的E'(2)刚性模式吸收峰强度可达最大值,这一过程与GaSe∶Te晶体光学性能的提高密切相关。但Te掺杂浓度的进一步提高会导致E'(2)刚性模式吸收峰强度逐渐减弱,当Te掺杂浓度为1%时,E'(2)刚性模式吸收峰基本消失。这两个过程与GaSe∶Te晶体光学质量的下降密切相关。因此,E'(2)刚性模式吸收强度达到最高时对应的掺杂浓度即是GaSe∶Te晶体中Te的最佳掺杂浓度,光整流产生太赫兹过程证实了此结论的正确性。 相似文献
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Alwyn G. Davies R.W. Dennis D. Griller K.U. Ingold B.P. Roberts 《Molecular physics》2013,111(4):989-991
Clementi and Veillard's analysis of the MC SCF theory of closed-shell systems is developed on a different basis. An equivalent Hartree-Fock operator is defined and its physical significance is discussed. A generalized Brillouin theorem is derived, different from that given by Levy and Berthier. 相似文献
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古新安 朱韦臻 罗志伟 ANGELUTS A A EVDOKIMOV M G NAZAROV M M SHKURINOV A P ANDREEV Y M LANSKII G V SHAIDUKO A V KOKH K A SVETLICHNYI V A 《中国光学》2012,5(1):57-63
从GaSe∶AgGaSe2熔体(质量掺杂浓度为10%)中生长的非线性光学晶体ε-GaSe∶Ag晶体(质量掺杂浓度≤0.04%)是一种非中心对称晶体,可用于相位匹配频率转换。Ag的掺入使GaSe晶体的显微硬度提高了30%,从而使其可以在任意方向上进行切割和抛光。本文研究了GaSe∶AgGaSe2晶体在可见、中红外及太赫兹波段的光学性能。实验证明:GaSe∶AgGaSe2晶体的吸收系数是纯GaSe晶体的2倍,其CO2激光倍频效率是ZnGeP2晶体的1.7倍。 相似文献
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Johnson SL de Souza RA Staub U Beaud P Möhr-Vorobeva E Ingold G Caviezel A Scagnoli V Schlotter WF Turner JJ Krupin O Lee WS Chuang YD Patthey L Moore RG Lu D Yi M Kirchmann PS Trigo M Denes P Doering D Hussain Z Shen ZX Prabhakaran D Boothroyd AT 《Physical review letters》2012,108(3):037203
We report on the ultrafast dynamics of magnetic order in a single crystal of CuO at a temperature of 207 K in response to strong optical excitation using femtosecond resonant x-ray diffraction. In the experiment, a femtosecond laser pulse induces a sudden, nonequilibrium increase in magnetic disorder. After a short delay ranging from 400 fs to 2 ps, we observe changes in the relative intensity of the magnetic ordering diffraction peaks that indicate a shift from a collinear commensurate phase to a spiral incommensurate phase. These results indicate that the ultimate speed for this antiferromagnetic reorientation transition in CuO is limited by the long-wavelength magnetic excitation connecting the two phases. 相似文献