离子速度影像法研究n-C7H15Br分子光解反应动力学

利用离子速度成像方法, 研究n-C7H15Br分子在231～239 nm范围内几个波长处的光解离动力学. 通过同一束激光经(2+1)共振多光子电离(REMPI)过程探测光解碎片Br(2P3/2)和Br*(2P1/2), 得到了不同激光波长处的离子速度分布图像, 从而获得C7H15Br光解产物的能量分配和角度分布. 结合各向异性参数和量子产率, 计算了n-C7H15Br分子在234 nm波长下不同解离通道的比例. 实验表明光解产物的能量分配可以用冲击模型中的软碰撞模型来解释. 实验还发现, 各向异性参数β(Br*)的值对光波长变化很敏感, 这是由电子激发态的绝热和非绝热过程决定的.     

正-溴代烷烃的紫外光解动力学研究

利用共振增强多光子电离飞行时间质谱(REMPI-TOFMS)，研究了长链正-溴代烷烃R-Br(R为正烷烃基)(C2H5Br，n-C3H7Br，n-C4H9Br)在234及267nm附近的光解动力学．溴碎片来源于R-Br的直接解离：R-Br→R Br(^2P3/2)／Br(^2P1/2)，根据测定的离子信号强度，得到了Br^n与Br的分支比N(Br^*)／N(Br)及相应的相对量子产额φ(Br^*)和φ(Br)．φ(Br^*)与激光波长及分子结构显示了一定的依赖关系，将实验结果用CH3Br的解离模型进行拟合，得到了长链R-Br的光解动力学行为的定性解释。     

离子速度成像方法研究C8H17Br分子的光解动力学

用离子速度成像方法, 研究了长链C8H17Br分子在234 nm激光下的光解过程. 通过2+1共振增强多光子电离探测了两种光解产物Br*(2P1/2)和Br(2P3/2), 得到了它们的相对量子产率. 从光解产物Br*(2P1/2)和Br(2P3/2)的速度图像得到了能量和角度分布. 并根据相对量子产率和角度分布, 计算了不同解离通道的比例. 实验发现C8H17Br分子解离过程中大部分能量都转化为内能, 该能量分配可以较好地用软反冲模型来解释, 并分析了这种能量分配跟烷基大小的关系.     

离子速度成像方法研究溴代环己烷的紫外光解动力学

利用二维离子速度成像方法对C6H11Br分子在234 nm附近的光解动力学行为进行了研究. 通过(2+1)共振增强多光子电离探测了光解产物Br*(2P1/2)和Br(2P3/2), 得到它们的相对量子产率. 从光解产物Br*(2P1/2)和Br(2P3/2)的速度图像得到了能量和角度分布. 结果表明, Br*原子主要来自于S1态的直接解离, 而Br则绝大部分是从S2态向T3态的系间交叉跃迁得到, 并导致了两种解离通道能量分布的差别. 实验发现C6H11Br分子解离过程中大部分能量都转化为内能, 但与其它长链溴代烷烃分子相比, 可资用能更多地被分配到平动能中, 结合软反冲模型分析了这种能量分配跟环烷基的构象和稳定性的关系.     

二溴代烷烃的紫外光解动力学研究

利用飞行时间质谱装置研究了234和267nm激光作用下二溴甲烷、二溴乙烷、二溴丙烷和二溴丁烷分子的光解离过程．研究表明二溴代烷烃分子在紫外激光的作用下主要是断裂C—Br键解离出一个Br原子，并且存在两种可能的布居：基态Br(^2P3/2^0)和激发态Br^*(^2P1／2^0)．通过共振增强多光子电离技术探测两种光解产物布居的分支比．对比得到了分子构型对称性不同的二溴代烷烃的分支比，提出了两种假设的光解离模型．     

CH2BrCl在265 nm光解产生的氯甲基自由基的振动内能

利用离子速度影像技术研究了CH2BrCl在265nm附近的激光光解.利用2+1共振增强多光子电离分别获得光解产物Br(2P1/2)和Br(2P3/2)的离子速度图像,从而得出Br(2P1/2)和Br(2P3/2)的速度分布,以及光解碎片的总平动能分布.据此,运用角动量守恒碰撞模型获得了解离氯甲基自由基(·CH2Cl)的振动内能分布.研究结果表明:CH2BrCl+hv→Br(2P1/2)+CH2Cl通道产生的氯甲基自由基中被激发的振动模主要是v4、v3+v4、v2+v4和v2+v6;CH2BrCl+hv→Br(2P3/2)+CH2Cl通道产生的氯甲基自由基中被激发的振动模主要是v2+v6、v1+v3、v2+v5、v2+v3+v5和v1+v5;母体分子CH2BrCl在吸收光解光子后除有v5(CBrstretch)振动模被激发外,还有v7(CH2a-stretch)等其它振动模也被激发.     

催化裂解富气吸收液的离子色谱法测定

以催化裂解富气吸收液为测定对象，建立吸收液中目标离子（包括NO2^-，NO3^-，SO4^2-）的离子色潜分析方法。在选定色谱柱的前提下，通过优化淋洗液浓度等色谱条件，实现了在大量干扰离子S^2-及与SO4^2-相邻的未知离子存在的三乙醇胺溶液中目标离子的定量。方法的检出限分别为NO2^- 62μg／L，NO3^- 26μg／L，SO4^2- 90μg/L，RSD值为0．73％～1．19％，加标回收率在91％～109％。     

离子色谱法测定饮用水中无机消毒副产物

采用直接进样离子色谱法,对饮用水中无机消毒副产物(DBP):ClOˉ2、BrO、ClOˉ3和Brˉ进行分离检测;研究了分离柱的选择、淋洗液的浓度和流速对分离的影响;在优化的条件下,4种离子的工作曲线范围为1．0～50μg／L;检出限为ClOˉ2 0.3μg／L、BrOˉ3 0.6μg／L、ClOˉ3 0.9μg／L和Brˉ0.6μg／L;4种离子的RSD(n=8)分别为3．8％、3．6％、4．0％和5．0％;本法操作简单、运行费用低、灵敏度高,应用于饮用水的分析。结果令人满意。     

SO3／γ-Al2O3固体酸催化剂的制备、结构与酸性表征

用酸中和法制备了活性γ-Al2O3，并在其表面负载SO3得到固体酸催化剂SO3／γ-Al2O3，用XRD，TG-DTA，FT-IR，NMR，NH3-TPD等对其进行了结构和酸性研究．结果表明：在SO3／γ-Al2O3的制备过程中形成少量的Al2(SO4)3，同时SO3与γ-Al2O3表面上的羟基反应，形成强的Br（oe）nsted酸位，根据^1H／^27Al双共振（TRAPDOR)MAS NMR与FT-IR实验结果提出了Br（oe）nsted酸结构模型．SO3／γ-Al2O3表面存在两种不同强度的酸中心，其酸强度大于分子筛HZSM-5，但弱于传统的固体超强酸SO4^2-／γ-AL2O3．     

邻溴甲苯在234和267 nm的光解动力学

利用离子速度影像技术结合共振增强多光子电离(REMPI)技术, 研究了邻溴甲苯在234和267 nm激光作用下的光解机理. 平动能分布表明, 基态Br(2P3/2)和自旋轨道激发态Br*(2P1/2)产生于两个解离通道: 快通道和慢通道. 快通道的各向异性参数在234 nm分别为1.15(Br)和0.55(Br*), 在267 nm分别为0.90(Br)和0.60(Br*). 慢通道的各向异性参数在234 nm分别为0.12(Br)和0.14(Br*), 在267 nm分别为0.11(Br)和0.10(Br*). 源自于慢通道的Br和Br*碎片的各向异性弱于快通道. Br(2P3/2)的相对量子产率Φ(Br)在234 nm为0.67, 在267 nm为0.70. 邻溴甲苯在234 和267 nm光解主要产生基态产物Br(2P3/2). 快通道产生于(π, π*)束缚单重态被激发, 随后通过排斥性(n, σ*)态的预解离. 慢通道各向异性参数接近零, 由此证实慢通道来源于单重激发态内转换到高振动基态而引发的热解离.     

铵盐离子对中有机阴离子交换排序的研究

本文用测定ClO_4~-离子选择性电极电势选择性系数K_(ij)~(pot)的方法,研究了七种长链季铵大阳离子与十余种有机阴离子在水、油两相中交换能力的排序。即: C_2O_4~-相似文献   

铜离子印迹聚合物的吸附性能研究EI北大核心CSCD

以二苯氨基脲为功能单体,合成了铜离子印迹聚合物(Cu^(2+)-IIPs),并用于Cu^(2+)的快速吸附检测。对Cu^(2+)-IIPs进行了表征,考察了其对Cu^(2+)的吸附特性。结果表明,Cu^(2+)-IIPs为球型状颗粒且粒径分布均匀,印迹位点位于表面及空穴中,对Cu^(2+)的吸附过程符合准二级动力学模型,吸附速率受表面吸附和内部扩散共同影响。较之Langmuir模型和Tempkin模型,Freundlich模型能更好地拟合吸附等温线,说明属于多层吸附;ΔG^(0),ΔH^(0)和ΔS^(0)的数据显示,吸附是一个自发进行的、吸热的、熵增大的过程;Cu^(2+)-IIPs对Cu^(2+)的吸附量远大于具有相似结构和性质的其它重金属离子,因而具有良好的吸附选择性。     

In defense of the quasimolecular ion

The term quasimolecular ion has been used to describe ions comprising a molecule and weakly bound positive or negative ion or an ion formed by the loss of a proton from a molecule. This term was used in mass spectrometry from the late 1960s after the development of chemical ionization but has been deprecated in recent terms recommendations due to what is perceived as its overly broad use. This letter argues that the term is well defined and has a long history of use in mass spectrometry and other fields and should be considered as a recommended term.     

The effect of potential on the gold dissolution in cyanide solutions in the presence of sulfide ions

The effect of potential on the rate of gold dissolution in the cyanide solutions in the presence of sulfide ions is studied. The dependences of current on the time after the electrode surface renewal were measured under the potentiostatic conditions. The majority of experiments were performed in the solution of the following composition, M: 0.1 KCN, 0.1 KOH, 0.01 KAu(CN)₂, (1.5–2) × 10^?5 Na₂S at 23°C. It is shown that, at the potentials more positive than ?0.1 V (NHE), the rate of gold dissolution starts to increase as soon as the surface is renewed, which is associated with high-rate chemisorption of catalytically active sulfide ions. At E < ?0.1 V, the chemisorption proceeds slowly, and a considerable increase in the current takes much time. Therefore, in the potentiodynamic measurements, at E < ?0.1 V, no catalytic effect of sulfide ions is observed. When the ratio between the concentrations of sulfide and cyanide ions is decreased, the potential, which, by convention, bounds the aforementioned ranges, shifts in the positive direction. Plausible explanations for these regularities are proposed.     

A theoretical study of the electromagnetic properties of ferrocene and the ferrocenium ion

An iterative extended Hückel molecular orbital calculation was used to obtain wave functions for the ground state of ferrocene and several low lying states of the ferrocenium ion. Photoemission spectra in terms of relative ionization potentials and the electric field gradient at the iron nucleus were calculated for ferrocene andg values and the electric field gradient were calculated for the ferrocenium ion. These values are in good agreement with experiment. The nature of the molecular orbitals was compared with results of previous semi-empirical andab initio calculations.     

共掺稀土离子对Er~(3+)激活中红外激光晶体光谱性能的影响

Er3+掺杂的晶体能够产生2.7~3.0μm波段中红外激光,在激光医疗、光通讯、环境探测和光电对抗等领域具有重要的应用。基于本课题组近年来开展的Er3+激活中红外激光晶体的相关工作,本文综述了共掺稀土离子对Er3+激活晶体光谱性能的影响:包括敏化离子Cr3+、Yb3+等的敏化作用增强了Er3+的特征吸收峰;退激活离子Pr3+、Ho3+等的退激活效应抑制了自终态瓶颈效应;以及共掺Nd3+所起的敏化和退激活双重作用,并对中红外激光的研究趋势和前景进行了展望。     

Direct Determination of Cu2+ Based on the Electrochemical Catalytic Reaction of Fe3+/Cu2+

Copper ion (Cu²⁺) is one of the heavy metal ions which has been considered as a severe pollutant affecting the environment and human health. Therefore, it is necessary to detect Cu²⁺ sensitively and conveniently in food and drinks. However, the gold standard method that inductively coupled plasma mass spectrometry (ICP‐MS) is expensive equipment required and time‐consuming. In this work, a highly sensitive and facile electrochemical method was studied to directly determine the concentration of Cu²⁺ without cumbersome modification on the surface of glassy carbon electrode (GCE). In the presence of ferric ion (Fe³⁺), Cu²⁺ could play a role of catalyst in the detection system, and the electrochemical signal of differential pulse voltammetry (DPV) response to Cu²⁺ could be amplified obviously. Under the optimal conditions, a good linear relationship was obtained in the range of 1 nM to 5 μM with a detection limit of 57.5 pM (S/N=3) were obtained. Besides, the proposed method has good applicability for the detection of Cu²⁺ in tap water. Furthermore, the copper complex was detected and the results were indicated the proposed method was effective and sensitive.     

复杂离子反应的规律及其离子方程式书写策略

基于中学教学实际，针对师生对复杂离子反应及其离子方程式书写的困惑，通过整理和归纳，把复杂离子反应分为连锁反应、并列反应和竞争反应等3种反应类型，探究了复杂离子反应的规律、分析策略、离子方程式书写的方法及应用。     

有机酸对离子色谱法测定氟离子的影响

比较了不同体系下离子色谱法测定考核样中氟离子的准确度。在碳酸盐–碳酸氢盐体系下分析氟标准样品,进行甲酸根、乙酸根加标试验,讨论了甲酸根、乙酸根对氟定量准确性的影响。考核样品色谱峰处理前氟测定结果为0.273 mg/L,与统计均值0.240 mg/L相比偏高,色谱峰处理后结果为0.243 mg/L,在统计Z值偏差范围内。同时在氢氧根体系下分析考核样品,有效改善了氟离子与乙酸、甲酸的分离度。在氢氧根体系下分析环境水样中低浓度氟离子快速、方便。     

Salt effects in the mercuration of unsaturated compounds. Kinetic evidence for the formation of ion pairs and a solvated ion

The kinetics of mercuration of bornylene and cyclohexene in different solvents in the presence of NaOAc and LiClO₄ has been investigated. Addition of NaOAc sharply decreases the rate of addition reactions of mercuric acetate to bornylene and cyclohexene in alcohols; the main direction of the mercuration of bornylene is the formation of acetoxy-adducts, and the yield of solvo-adducts decreases from 76 % in the absence of NaOAc, to 19 % in the presence of the salt (4·10^–3 mol L^–1). A reaction scheme involving the participation of intermediate ion pairs and a solvated mercurinium ion is suggested and confirmed by a steady-state concentration method. The influence of NaOAc on the rate of the reaction and on product formation is realized through the common ion effect.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 819–826, May, 1994.