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在大于300nm光波照射下,氯化亚铜或乙酰丙酮基铜(I)等低价铜配合物可以有效地催化中大环环状烯烃的顺、反异构化反应,对在大于250nm光波照射下,顺,顺-1,5-环辛二烯分子内环加成形成三环[3.3.0.0^2^.^6]-辛烷的反应机制,进行了讨论。 相似文献
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Autooxidation processes of free radicals trapped in γ irradiated F46 copolymer in vacuum at room temperature were studied by means of ESR. It is shown that these processes are under the dual control of both the diffusion of oxygen and the total concentration of free radicals, and they are independent of the autooxidation reaction rate constant. In general, the diffusion constant calculated by simple diffusion equation is an apparent diffusion constant, it is a function of the total concentration of free radicals. Only when the total concentration of free radicals is low enough (in our case n-2X10^1^7 spins/g), the apparent diffusion constant is close to its real value on unirradiated sample. By the method given in this paper, the diffusion constant of oxygen has been calculated to be 1.6X10^-^7 cm^2/sec at 20`C for F46 film obtained by suspension polymerization. 相似文献
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The chemical processes of tryptophan (Trp), tyrosine (Tyr) and a dipeptide Trp-Tyr, which are induced by UV radiation and one-electron oxidation of SO.
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–, have been investigated in aqueous solution by KrF (248 nm) laser flash photolysis. On the basis of optical studies, the photoionization of Trp and Tyr produces the tryptophan indolyl radical and tyrosine phenoxyl radical, respectively, and these are different from the intermediates resulting from interaction of Trp and Tyr with SO.
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–. In the case of Trp, SO.
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– would attack the indole moiety to produce a C(2)-yl sulphate radical adduct, and Tyr is oxidized to produce mainly the corresponding one-electron oxidized radical, which deprotonates rapidly to form the phenoxyl radical in neutral solution, and a possible sulphate radical adduct. From transient absorption spectra of photoionization of Trp-Tyr, an intramolecular electron transfer, Trp/N.-Tyr Trp-Tyr/O., has been observed, but there was no observation of the process of one-electron oxidation of Trp-Tyr by SO.
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–. 相似文献
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激光-时间分辨荧光法测定U3O8中痕量硼 总被引:2,自引:0,他引:2
本文提出了一种测定U3O8中痕量硼的激光-时间分辨荧光法, 在适当介质中, 用小型氮分子激光器激发硼与二苯甲酰基甲烷配合物的荧光, 发现此配合物的荧光寿命为2ms, 它比铀的荧光寿命长得多, 从而可将荧光的时间分辨技术应用于铀中硼的测定, 不经分离基体铀即可进行测定, 方法简单而快速, 检测下限达到0.02ng.mL^-^1(硼),当取样10mg铀时, 能测定0.01ppm的硼。用本法分析了含量在0.04-0.5ppm几个U3O8样品, 结果与其他方法相符。 相似文献
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采用探测室可转动的分子束实验装置,研究了氯分子束与GaAs(100)表面热反应和紫外激光诱导反应的动力学.结果表明,热反应的主要产物为GaCl~3, 其角分布可用cos^2^.^3θ函数拟合.对于紫外(355nm)激光诱导反应,由角分辨的飞行时间(TOF)法测得主要产物为GaCl等,它们的通量角分布须用双余弦加和公式(c~1cosθ+c~2cos^nθ)拟合,表示产物粒子在表面法线方向明显聚集,而且由TOF 谱求得粒子的动能在表面法线方向最大. 这种明显的聚集现象可以由激光诱导的粒子在表面附近发生碰撞效应来解释 相似文献
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应用10~(-12)s级时间分辨率的荧光光谱,测定了两种碳菁染料和一种荧光素染料(四碘荧光素B)的荧光寿命τ与溶剂粘度η之间的函数关系,发现碳菁染料在二元醇和丙三醇中的τ_(FM)低得反常.在二元醇溶剂中,它们的τ_(FM)与溶剂粘度η~(2/3)呈线性函数关系,但在一元醇溶剂中则并无此线性关系.由此可见,在研究染料分子的寿命与由不同系列醇(例如乙醇和丙三醇)组成的混合溶剂的粘度之间的依赖关系时,必须十分谨慎.对于四碘荧光素B,它在一元醇中的荧光寿命与溶剂粘度的关系符合2/3指数规律. 相似文献
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