—氯甲烷同步辐射光电离研究——离子生成焓与键能的测定

本文报道超音速射流冷却条件下,用同步辐射光研究CH_3Cl光电离及其解离电离的动力学,测得CH_3Cl的电离能(IP)为11.28±0.01eV.通过测定CH_3Cl光解离电离碎片的出现势(AP),并结合有关已确认的热力学数据,获得了它们的标准生成焓、离子型分子中的键能、中性分子或自由基中的键能及母体离子的解离能等热力学数据.对CH_3Cl分子VUV光解离电离通道进行了分析.     

CH3I同步辐射光电离及生成焓、键能和质子亲合势的测定

在超声射流冷却条件下用VUV同步辐射研究了CH3I分子的光电离过程。测定了CH3I光电离及解离电离产生的CH3I^+, CH3^+和I^+的出现势, 结合已确认的热力学数据, 估算出体系中有关离子的标准生成焓、分子和分子离子的键能、自由基的质子亲合势及母体离子的解离能等数据。对CH3I分子VUV光解离电离通道进行了分析。     

3-氯-1，2-环氧丙烷的同步辐射光电离

杂环类化合物在自然界中分布十分广泛,且许多具有生物活性,它们大多数在生物的生长 发育、遗传和衰亡过程中起着关键的作用［１,２］．含氧三元杂环体系是最基本、最简单的杂环化合 物,分子中的含氧三员环,具有很大的张力,且存在很强的极性共价键,使其易于发生定向开环 反应,具有高度反应性．利用光电高质谱法对这类分子进行光电离与光离解研究,可以获得这 类物质一些重要的物理化学数据． 我们已对环氧乙烷和环氧丙烷进行了光电离和光离解研究,并结合量化理论计算分析了 它们的光电离解离通道［３,４］,３－氯－１,２－环氧丙…     

二溴甲烷的同步辐射光电离研究

采用５０～２００ｎｍ同步辐射光，对ＣＨ２Ｂｒ２的光电离过程进行了研究，根据测定的母体离子及其碎片离子出现势，得到二溴甲烷的绝热电离势为１０．２３±０．０１ｅＶ，并获得了离子的生成焓，解离能及键能等热力学数据，分析了碎片离子的光解离电离通道。     

环氧乙烷的真空紫外同步辐射光电离与光解离

利用真空紫外同步辐射和自制的飞行时间质谱（TOF－MS）仪,研究了环氧乙烷的光电离与光解离过程,通过测量各离子的光电高效率（PIE）曲线,获得了该分子的电离势和所有碎片离子的出现势．分析了离子的光电离解离通道,并讨论了它们的竞争情况．结合有关公认的热力学数据,算出它们的标准生成焓．     

对硝基甲苯的同步辐射光电离研究

光电离对硝基甲苯（PNT）可获得其电离势及碎片离子的出现势，并由此推断出离子产生的可能通道．目前尚未见到有关PNT光电离研究的报道，仅George等［‘j使用电子轰击电离质谱测得过它的电离势．我们使用同步辐射光电离质谱测得了PNT的电离势和8种碎片离子的出现势，给出了飞行时间（TOF）质谱图，归属了质谱中的主要离子峰，初步分析了光解离电离通道．1实验部分实验装置由阈值光电子一光离子符合（TPEPICO）装置改造而成［’，’］，光电离室上方的四极质谱计由TOF质谱计代替，下方的四极质谱计由盛固体样品的小炉取代．样品蒸…     

二茂铁的同步辐射光电离

The vacuum ultraviolet photoionization of ferrocene has been studied by using synchrotron radiation and a time-of-flight（TOF）mass spectrometer. The photoionization TOF mass spectrum and photoionization efficiency （PIE）curves of some ions were measured. VUV absorption by ferrocene results in Fe（C5H5）2+,FeC5H5+,Fe+,FeC3H3+,FeC3H+,C10H9+,C10H8+ and C5H6+. The ionization potential（IP）of ferrocene is determined to be （6.78±0.05）eV. The appearance potential（AP）of the fragment FeC5H5+ was measured to be（13.40±0.10）eV. In addition,theoretical calculations with the density functional method B3LYP and the basis set 6-31G（d）have been carried out. The calculation result shows that the ionization potential of ferrocene is 6.16 eV,which is smaller than that from the experiment because the ionization potential from calculation is adiabatic value and the experimental result is vertical value. Due to the limited available computational cost,the case of the electron spin S=1/2 for Fe is only considered,which may lead to some low precision in calculation. So the calculation result is just as references. The appearance potential of FeC5H5+ is 12.17 eV,which is also smaller than the experimental value. According to the experimental and calculation results,the bond energies of D0（FeC5H5+-C5H5）,D0（Fe+-C5H5）,D0（C5H5-Fe+-C5H5）have been evaluated and the possible channels of dissociation photoionization have been analyzed. Sequential elimination of C5H5 ligands is a major dissociation channel,but concerted elimination of two C5H5 ligands also takes place.     

结构参数X的计算方法及与分子总键能和生成焓的关系

本文借助于电负性I和有效主量子数n_i^*定义了有效价电子数Z_i′。由Z_i′、 n^*_i及成键电子数mi定义的原子结构参数δ_i和分子结构参数X被计算。发现A_mB_n型分子的X相似文献   

氯乙烯的同步幅射光电离及C-H和C-CI键离解能的测定

利用同步辐射对C~2H~2CI进行了光电研究,得到了电离势IP(C~2H~2CI)为10.03±0.01eV及其碎片的光电离出现势,导出了离解能D~0(C~2H~2CI-H),D~0(C~2H~2CI^+-H),D~0(C~2H~2CI-H^+),D~0(C~2H~2-CI)和D~0(C~2H~3^+-CI),它们的值分别为5.09±0.05,5.02±0.08,8.66±0.05,3.64±0.10和2.56±0.05eV.     

氯乙烯的同步幅射光电离及C-H和C-CI键离解能的测定

利用同步辐射对C~2H~2CI进行了光电研究,得到了电离势IP(C~2H~2CI)为10.03±0.01eV及其碎片的光电离出现势,导出了离解能D~0(C~2H~2CI-H),D~0(C~2H~2CI^+-H),D~0(C~2H~2CI-H^+),D~0(C~2H~2-CI)和D~0(C~2H~3^+-CI),它们的值分别为5.09±0.05,5.02±0.08,8.66±0.05,3.64±0.10和2.56±0.05eV.     

mezo-和d, l-2, 3-二氯丁烷气态生成焓的测定

本文用直接量热法测量了298.15K时meso-和d, l-2, 3-二氯丁烷的液态蒸发焓值以及其混合物的液态燃烧焓值, 得到了它们的标准气态生成焓值, 考察了二氯烷烃分子内氯原子间的相互影响和相互作用对其气态生成焓值的影响。     

2-氯丁烷、1,2=二氯丁烷气态生成焓的测量

用转动氧弹燃烧热量计测量了298.15K时2-氯丁烷和1,2-二氯丁烷的标准液态燃烧反应内能变化值,得到了它们的标准所态生成焓值,并进一步考查了二氯取代地氯代烷烃气态生成焓值的影响量.     

三氯苯的标准生成焓和异构化焓

报导了用精密转动弹量热计测定诸三氯苯燃烧热的实验结果,并计算出这些化合物在液态(或固态)和气态下的标准生成焓.同时还计算出它们的异构化焓和原子化热,并与一般公认为比较精确的热化学键能模式的计算值进行比较和讨论.     

卟啉化合物的热化学研究: V. 含溴卟啉化合物的标准燃烧能和生成焓

用本实验室建立的精密转动氧弹燃烧热量计测定了标准物质对溴苯甲酸、辅助物质鲨烷及四对溴苯基卟啉(Tp-BrPP)的标准燃烧能, 并计算出了它们的标准生成焓。     

硝酸钇水合物在水内的溶解热测定和标准生成热计算

本文测定了25℃时,Y(NO_3)_3·nH_2O(n=6,5,4)在0.219m以及Y(NO_3)_3·3H_2O从0.014m到0.219m的积分溶解热;推导了计算Y(NO_3)_3·3H_2O溶解热、硝酸钇溶液的稀释热以及硝酸钇相对表观摩尔焓和相对偏摩尔焓的经验公式.利用测得的溶解热数据,计算了这些水合物的标准生成热、脱水焓和晶格能.     

锕系配合物中Vander Waals能与配位键能之间的平衡I:

对铀的几个络合物的配位键和Van der Waals能之间的平衡进行分析研究,发现在配位原子间配合键能和最大Van der Waals引力能几乎一致,这有力地支持了堆积模型将成为这一模型进一步发展的基础.     

Bond dissociation energies and radical heats of formation in CH3Cl,CH2Cl2, CH3Br,CH2Br2, CH2FCl,and CHFCl2

An analysis of thermochemical and kinetic data on the bromination of the halomethanes CH_4–nX_n (X = F, Cl, Br; n = 1–3), the two chlorofluoromethanes, CH₂FCl and CHFCl₂, and CH₄, shows that the recently reported heats of formation of the radicals CH₂Cl, CHCl₂, CHBr₂, and CFCl₂, and the C? H bond dissociation energies in the matching halomethanes are not compatible with the activation energies for the corresponding reverse reactions. From the observed trends in CH₄ and the other halomethanes, the following revised ΔH°_f,298 (R) values have been derived: ΔH°_f(CH₂Cl) = 29.1 ± 1.0, ΔH°_f(CHCl₂) = 23.5 ± 1.2, ΔH_f(CH₂Br) = 40.4 ± 1.0, ΔH°_f(CHBr₂) = 45.0 ± 2.2, and ΔH°_f(CFCl₂) = ?21.3 ± 2.4 kcal mol^?1. The previously unavailable radical heat of formation, ΔH°_f(CHFCl) = ?14.5 ± 2.4 kcal mol^?1 has also been deduced. These values are used with the heats of formation of the parent compounds from the literature to evaluate C? H and C? X bond dissociation energies in CH₃Cl, CH₂Cl₂, CH₃Br, CH₂Br₂, CH₂FCl, and CHFCl₂.     

Complex formation between tryptophan-containing peptides and nucleic acids: Fluorescence decay studies using synchrotron radiation

Synchrotron radiation has been used to determine the fluorescence decay parameters of a tryptophan-containing oligopeptide, Lys-Trp-Lys, bound to nucleic acids. All fluorescence decay curves can be fitted by a sum of two exponentials. The two lifetimes very likely correspond to two conformational states of the oligopeptide. The mean fluorescence lifetime of the peptide is not markedly affected upon binding to nucleic acids even though the fluorescence quantum yield is strongly reduced. A model is presented that accounts for the existing fluorescence data: two consecutive complexes are formed both involving electrostatic interactions. In one of the complexes the tryptophyl ring is stacked with the nucleic acid bases and its fluorescence is completely quenched. The other complex emits a fluorescence having characteristics which are similar to those of the free peptide.