Shape resonances in slow electron scattering by aromatic molecules. I. Anthraquinone derivatives

A series of anthraquinone (C(14)O(2)H(8)) derivatives has been studied by means of electron capture negative ion mass spectrometry (ECNI-MS), photoelectron spectroscopy (PES), and AM1 quantum chemical calculations. Mean lifetimes of molecular negative ions M(-.) (MNI) have been measured. The mechanism of long-lived MNI formation in the epithermal energy region of incident electrons has been investigated. A simple model of a molecule (a spherical potential well with the repulsive centrifugal term) has been applied for the analysis of the energy dependence of cross sections at the first stage of the electron capture process. It has been shown that a temporary resonance of MNI at the energy approximately 0.5 eV corresponds to a shape resonance with lifetime 1-2.10(-13) s in the f-partial wave (l = 3) of the incident electron. The next resonant state of MNI at the energy approximately 1.7 eV has been associated with the electron excited Feshbach resonance (whose parent state is a triplet npi* transition). In all cases the initial electron state of the MNI relaxes into the ground state by means of a radiationless transition, and the final state of the MNI is a nuclear excited resonance with a lifetime measurable on the mass spectrometry timescale. Copyright 1999 John Wiley & Sons, Ltd.     

富硒蛹虫草试样中硒的形态分析

本文采用连续浸提法研究了富硒蛹虫草中硒的赋存形态。结果表明,碱溶态>盐溶态>水溶态>醇溶态>残渣态。可见,碱浸取是获取植物蛋白的有效途径,在富硒蛹虫草试样中硒主要以硒蛋白的形式存在。     

Determination of electron affinity of carbonyl radicals by means of negative ion mass spectrometry

Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd.     

Strong field ionization to multiple electronic states in water

High harmonic spectra show that laser-induced strong field ionization of water has a significant contribution from an inner-valence orbital. Our experiment uses the ratio of H(2)O and D(2)O high harmonic yields to isolate the characteristic nuclear motion of the molecular ionic states. The nuclear motion initiated via ionization of the highest occupied molecular orbital (HOMO) is small and is expected to lead to similar harmonic yields for the two isotopes. In contrast, ionization of the second least bound orbital (HOMO-1) exhibits itself via a strong bending motion which creates a significant isotope effect. We elaborate on this interpretation by solving the time-dependent Schr?dinger equation to simulate strong field ionization and high harmonic generation from the water isotopes. We expect that this isotope marking scheme for probing excited ionic states in strong field processes can be generalized to other molecules.     

Reactions of Me2Si(2‐Me‐4,5‐BenzInd)Zr(Cl)(NEt2) and Me2Si(2‐Me‐4,5‐BenzInd)ZrCl2 (BenzInd = benzindenyl) with trimethylaluminum and methylaluminumoxane: Correlation of spectroscopy and propene polymerizations

The activity of metallocene/methylaluminumoxane (MAO) catalysts in olefin polymerization is highly dependent on both the alkylation and activation of the complexes. The leaving ligands have an important role in the complex activation, influencing the activity of the system. The aim of this work was to study the reactions of complexes Me₂Si(2‐Me‐4,5‐BenzInd)₂ZrCl₂ ( A ; BenzInd = benzindenyl) and Me₂Si(2‐Me‐4,5‐BenzInd)₂Zr(Cl)(NEt₂) ( B ) with trimethylaluminum (TMA) and MAO. The reaction kinetics and products were studied by both ultraviolet–visible and NMR spectroscopy. In addition, the polymerization behavior of the different species was investigated in propene polymerizations. Complex B was more easily monomethylated by TMA than complex A and resulted in L₂Zr(Me)(NR₂)‐type species. Monomethylation of the complexes before polymerization enhanced the polymerization activity of both complexes. When complexes A and B reacted with MAO, similar cationic species were formed, giving equal polymerization activities. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6455–6464, 2005     

PPT文件中的动画制作及在教学中的应用

介绍了利用PowerPoint软件的自定义动画中的"进入"、"强调"、"退出"、"动作路径"四类效果,制作教学中常用的化学结构式、图表、原理图、选择题等的动画制作的方法,以及常用图表的讲解、重点内容的强调、利用现有矢量性质剪帖画改制成自己所需图画的简易方法.PPT文件制作动画,操作简单,避免了超链接的麻烦,形成的文件小,便于拷贝,可制作出具有Flash效果的漂亮、生动的动画,丰富了教学内容、提升了教学效果.     

Influence of meta-extended rigid-core,complementary hydrogen bonding and flexible chain on polymorphism in Schiff-base liquid crystals: (4)MeOBD(3)AmBA:nOBAs

ABSTRACT

Schiff-base complementary hydrogen-bonded liquid crystals (HBLC), viz., (4)_MeOBD(3)_AmBA:nOBAs with flexible chain length for n = 3,4,5,6,7,8,9,10,11 and 12 are reported. ¹H; ¹³C-NMR and Infra-Red spectroscopy used to confirm the formation of HBLCs. LC phases and transition temperatures (T_c) determined by polarised optical microscopy (POM) and differential scanning calorimetry (DSC). T_c and enthalpy (?H) determined by DSC also. Odd-Even effect observed at clearing and melting transitions. Influence of Schiff base and Oxygen as bridging atom promote smectic phase abundance. HBLCs exhibit tetra- or penta-phase variance. Maximum (penta) phase variance is exhibited by n = 8 and 12 with long flexible chain. Prevalent abundance of quasi-two-dimensional (2D) LC phases of SmF and SmI is observed. Nematic phase is quenched. Lower (n = 4) and intermediate (n = 6) members exhibited SmB_cryst phase. Predominant occurrence of enantiotropic LC phases is noticed. All members exhibited 3D tilted SmG phase. A-C transition exhibited by intermediate homologues (for n = 7, 8, 9 and 10) is found to be either second order or with very small enthalpy. Phase diagram reveals the abundance of multi-critical points with LC phasesinvolving exotic symmetries. Influence of meta-extended rigid core, complementary HB and flexibility is studied for the LC phase abundance with characteristic structural order. POM and DSC results are discussed in the wake of reports in other achiral calamitic LCs.