光电子成像方法研究Xe时间分辨多光子电离过程

利用自行研制的离子成像检测器研究了Xe的飞秒时间分辨双色多光子电离过程.Xe的408nm多光子电离对比实验结果表明,该离子成像检测器与相应的进口产品具有相近的光电子能量分辨率.在272nm飞秒激光作用下,3光子电离产生能量为1.57和0.26eV的光电子,分别对应于Xe+的两个自旋态;在408nm飞秒激光作用下,还观察到第一级阈上电离产生的光电子.在双色飞秒时间分辨实验中,随着两束光相对时间的改变,光电子能谱出现了一系列的变化;随着两束光时间重合程度的增加,由双色多光子电离(3+1'或4'+1)产生的光电子信号逐渐加强;在第二束光的作用下,由第一束单色光产生的光电子出现能量红移,第二束光同时也导致中间态布居数减少.这种光电子能谱的红移现象反映了原子体系中激光场诱导有质动力势的时间分辨动态调制过程.     

一种新型细梗胡枝子黄酮类提取物的结构和抗氧化活性(英文)

利用密度泛函理论的B3LYP交换相关泛函对从细梗胡枝子中提取的一种新型黄酮类化合物的分子结构和抗氧化活性进行了研究,获得了该化合物的中性分子、阴离子、自由基和自由基阳离子的稳定几何构型和能量.通过分析前线分子轨道特征,确定了与实验结果一致的现象:A环是参加化学反应的活性部位,并发现A′环也是重要的抗氧化活性部位.为判断其抗氧化活性,预测其水溶液中,中性和阴离子的电离势分别为509.0和432.2kJ.mol-1,均裂O—H键解离能为347.3kJ.mol-1,羟基自由基电子亲和势和氢原子亲和势分别为-620.6和-487.5kJ.mol-1.通过理论分析比较,该黄酮类化合物清除羟基自由基的三种机理即H原子转移、电子转移-质子转移和质子丢失-电子转移在热力学上并存,其中质子丢失-电子转移是热力学最有利的机理.本文为设计新型高效黄酮类抗氧化剂,研究黄酮类化合物的构效关系和抗氧化机理提供了理论依据.     

高功率微波大气传输电离过程的物理研究

 指出平面1维近似不符合在远场处微波单位面积能流与传输距离平方成反比的规律。给出了束流1维近似下微波大气传输的基本方程组。详细研究了微波电离大气的特性和相似律。估计了平面1维近似下和束流1维近似下的尾蚀，指出当无量纲电离电子数不太小时，两者可能有很大差别。     

OCS的多光子电离高分辨光电子能谱

硫氧化碳OCS是线性三原子分子，这类小分子的激发态、离子态能级结构、能级之间的相互作用及电离过程，是研究中所关心的问题．Tanaka等[1]和Kopp[2]测量了OCS的VUV吸收光谱，Frey和Schlag等[3]以同步辐射光源，用光电离共振（PIR）谱方法、Kovac[4]和Wang，Shirley等[5]以Hel为电离光源，分别采用传统的光电子能谱和高分辨光电子能谱技术研究了CO2、CS2和OCS分子从电子振动基态吸收单个光子而电离的过程．Yang和Anderson等问为了作选态的离子一分子反应利用可调谐激光rt光子吸收将OCS选择激发到某一中间态，OCS再吸收光子后…     

Experimental and theoretical study of the electronic structure of methyl chloroformate and methyl cyanoformate

The HeI photoelectron spectra of methyl chloroformate (CH₃OC(O)Cl) and methyl cyanoformate (CH₃OC(O)CN) in the gas phase have been obtained for the first time. A complete theoretical study involving the calculation of the ionization energies using outer valence Green’s functional (OVGF) was performed, based on the calculated and previously reported energetically favorable cis-conformer (the carbonyl group eclipses the methyl group). Calculations of cationic-radical forms were carried out in order to interpret the main characters of the first six highest occupied molecular orbitals (HOMOs). The first vertical ionization potentials are 11.36 eV for CH₃OC(O)Cl and 11.65 eV for CH₃OC(O)CN, each attributed to {19a′(n_O(CO), n_Cl)}⁻¹ and {18a′(n_O(CO))}⁻¹, respectively.     

呋喃分子多光子电离解离过程的反应通道

The multiphoton ionization and fragmentation pathway of furan at 450nm is analyzed on the basis of statistical theory and Ladder-Switching model. Our calculation indicates that fragmentation takes plase after furan molecules absorb six photons of 450nm, C+ begins to appear after absorption of nine photons, production of C2+ ions needs absorption of at least 15 photons. Our interesting result is that C+ ions is produced by dissociation of C3H+, CH2+ and C3+ ions, not of C2+ ions. Theoretically computed relative abundance of C+/C2+ after absorption 15photons agrees well with our experimental results.     

The first ionization constant from 25 to 200°C and 2000 bar for orthophosphoric acid

The ionization constant of orthophosphoric acid, determined by conductivity measurements, decreased from 7.11×10^–3 at 25°C to 6.2×10^–4 mol-kg^–1 at 200°C. The pressure effect to 2000 bar was also measured and the ratio K₂₀₀₀/K₁ is 2.7 at 25°C and 3.7 at 200°C. The standard partial molar volume change for the ionization at 1 bar, , changes from –16.1 at 25°C to –33.3 cm³-mol^–1 at 200°C. The partial molar compressibility change for the ionization, , varies from –3.8×10^–3 to –8.3×10^–3 cm³-mol^–1 bar^–1 over the same temperature range.     

甲胺分子多光子电离质谱研究

胜多光子电离飞行时间质谱法，利用可调谐脉冲激光器，测得了甲胺分子在不同激光波长和激光功率下的多光子电离和解离产物。母体离子ＣＨ３ＮＨ＾＋２的离解速常数随激光发波长的增大而减小。     

The multiconfigurational spin tensor electron propagator method (MCSTEP): Comparison with extended Koopmans' theorem results

Summary We applied the multiconfigurational spin tensor electron propagator method (MCSTEP) for determining the lowest few (in energy) vertical ionization potentials (IPs) of HF, H₂O, NH₃, CH₄, N₂, CO, HNC, HCN, C₂H₂, H₂CO, and B₂H₆. We chose these molecules so that we could compare MCSTEP IPs with recently reported extended Koopmans' theorem (EKT) IPs on the same molecules. Using standard Dunning core-valence basis sets with relatively small complete active spaces, MCSTEP results are in very good to excellent agreement with experiment. These MCSTEP IPs are obtained using matrices no larger than 400 × 400. EKT matrices are even smaller; however, to obtain similar but generally slightly worse agreement with experiment, fairly large active spaces are required with EKT.     

Synthesis and Properties of Glass-Forming Hydrazones II [1]. Hydrazones Containing Bicarbazolyl Units

Summary.  A series of new glass-forming hydrazones containing bicarbazolyl units were synthesized starting from 9-(2-(9H-carbazol-9-yl)-cyclobutyl)-9H-carbazole and 9-(6-(9H-carbazol-9-yl)-hexyl)-9H-carbazole, and their thermal properties were studied. The correlation between their inclination to form glasses and their chemical structures are discussed. The results of a preliminary investigation of the photoelectric properties of amorphous films of the title compounds are briefly reported. The highest hole drift mobility was observed for 9-(2-(9H-carbazol-9-yl)-cyclobutyl)-9H-carbazole-3-carbaldehyde N,N-diphenylhydrazone; at high electric fields, it approaches 1 · 10⁻³ cm²/Vs. Received September 17, 2001. Accepted (revised) October 16, 2001