全角度（e，2e）电子动量谱仪的研制及若干分子的电子结构研究

【作者】 王克栋；

【导师】 陈向军；

【作者基本信息】 中国科学技术大学 ， 原子与分子物理， 2009， 博士

【摘要】 本论文报道了作者在博士研究生期间的主要研究工作,分为两部分;第一部分详细论述了我们新研制的一台高符合计数率的全角度（e,2e）谱仪,包括以下四章内容:第一章介绍电子动量谱学的（e,2e）反应原理、理论基础、实验安排、研究进展及其发展前景;第二章介绍全角度（e,2e）谱仪实验装置。介绍了谱仪的设计总体思想,并具体介绍了谱仪采用的关键实验技术及各组成部分,包括鼓型能量分析器,电子光学透镜系统、供气系统、磁屏蔽设施、真空系统以及供电系统等.第三章介绍了全角度（e,2e）谱仪的关键器件,双半圆楔条形阳极读出的位置灵敏探测器以及谱仪的前端电子学系统和基于PXI总线的在线数据获取系统。内容包括双半圆楔条形阳极的工作原理、影响分辨的因素、设计方法、具体制作工艺、解码公式的推导、机械装架和信号的读出等。此外,我们还对楔条形阳极的调制效应进行了实验和理论的研究,对谱仪的位置灵敏探测器的性能进行了测试和检验,得到了较为理想的二维位置图像,获得了良好的位置线性及位置分辨。第四章详细介绍了谱仪的调试及性能测试。初步对单路性能以及谱仪的整体性能进行了刻度和测试,获得了较为满意的结果。在通过能为600 eV时,单路的能量分辨约为1.5 eV,谱仪的符合时间分辨约为7 ns,符合能量分辨为2.1 eV,同时测量的相对方位角约为±130°,基本实现了全角度的测量。第二部分主要论述了利用电子动量谱手段和量子化学从头计算理论对二氟二溴甲烷的电子动量分布、乙醇胺和N,N-二甲基乙醇胺的电子结构进行的研究,主要包括以下四章内容:第五章简单介绍了计算中用到的基本理论方法,包括Hartree-Fock理论、密度泛函理论、自然键轨道理论等。第六章介绍利用能量多道的第二代（e,2e）电子动量谱仪结合理论计算对CF₂Br₂分子的电子结构进行研究,首次从实验上获得了CF₂Br₂分子外价壳层轨道的电子动量分布,全面研究了价轨道的排序,澄清了电离能谱上～15.5 eV的谱带指认存在的争议,并将其标识为5a₁和3b₁轨道电离。获得了内壳层1b₂轨道电离跃迁的极强度。第七章和第八章介绍采用密度泛函理论（DFT）和Mφller-Plesset（MP）微扰理论方法分别对乙醇胺的13种稳定构象和N,N-二甲基乙醇胺的12种稳定构象的研究。报道了存在稳定构象的几何构型和相对能量。采用电子传播子理论计算了各种稳定构象的电离能,理论模拟的电离能谱和实验光电子能谱吻合的很好,解释了HOMO和NHOMO电离能峰随着温度升高而移动的原因。结合自然键轨道理论分析,其本质是由于稳定构象的分子内氢键相互作用。论文的最后部分是对博士期间从事工作的总结及对未来工作的展望。更多还原

【Abstract】 This thesis presents my main research work as a Ph.D.candidate,which includes two parts:Part One mainly discusses the development of a high-coincidence-count 2π（e,2e） spectrometer which employs a series of key experimental techniques.This part includes four chapters as the following.In the first chapter,the principle of（e,2e） reaction,theoretical background, experimental arrangements,and the recent research progress of electron momentum spectroscopy（EMS） have been introduced.In the second chapter,the spectrometer has been described in detail.The different components of the spectrometer are respectively introduced,which includes the electron gun,a series of electron optical lens system,gas cell,analyzer,vacuum system,power supplies system,etc.In the third chapter,the key component of the spectrometer,a position sensitive detector（PSD） with a two-semicircle wedge and strip anode and multi-parameter data acquisition system have been designed and presented,which include the principle and facture of wedge and strip anode,output and process of signals from PSD,and experimental data acquisition.In addition,the performance of the two-dimensional PSD has been tested.The modulation effect has been simulated and the results are compared with the experiments.In the fourth chapter,the ways of adjustment and performance test of the spectrometer have been expatiated.The performance of the 90°sector energy analyzer has been tested by elastic scattering.The results show that the energy resolution of the analyzer is about 1.5 eV at passing energy of 600 eV.Moreover,at the incident electron energy of E₀= 1217 eV,the（e,2e） coincident time spectrum for Ar 3p ionization has been obtained.The time resolution is approximately 7 ns（FWHM）.At the same time,the binding energy spectrum for Ar 3p orbital has also been measured. The energy resolution is approximately 2.1 eV（FWHM）.The relative azimuth angle range of±130°for simultaneous detection has been achieve,which covers almost 2πangles.Part Two discusses the EMS study on dibromodifluoromethane（CF₂Br₂） and ab initio calculation studies on 2-aminoethanol（NH₂C₂H₄OH） and N,N-dimethylaminoethanol（N（CH₃）₂C₂H₄OH）.This part includes four chapters as the following.In the fifth chapter,the basic theoretical backfround used in this part is introduced including Hartree-Fock（HF） theory,density functional theory（DFT） and natural bond orbital（NBO） theory.In the sixth chapter,the measured electron momentum profiles of valence orbitals of CF₂Br₂ are compared with Hartree-Fock（HF） and density functional theory（DFT） calculations with different-sized basis sets.In general,the DFT-B3LYP calculation using the large basis sets of 6-311++G^** and aug-cc-pVYZ fairly describe the experimental results.Moreover,the controversial orderings of the outer valence orbitals have been reassigned.The pole strength of the main ionization transition from the inner valence orbital of lb₂ is determined.In the seventh and the eighth chapters,thirteen low-lying conformers of 2-aminoethanol（AE） and twelve low-lying conformers of N,N-dimethylaminoethanol （DMAE） are investigated using the density function theory（DFT） and M3/411er-Plesset perturbation theory calculations methods.The geometries and energies of all conformers are discussed.At the same time,the predicted IEs of low-lying conformers are used to assign the two lowest ionization bands in PES and to interpret the reason why the ionization bands moving with the temperature.Natural bond orbital（NBO） analyses exhibit a remarkable influence on the molecular electronic structures by the strong intramolecular HB OH…N and the relative weak intramolecular HB NH…O,leading to the significantly lowered energy levels of the occupied lone-pair molecular orbitals.更多还原