【作者】 黄艳茹；

【导师】 邓景康；

【作者基本信息】 清华大学 ， 物理学， 2008， 博士

【摘要】 电子动量谱学(Electron Momentum Spectroscopy, EMS)以其特有的同时测量物质中电子的能量分布和动量分布的优势,已发展成为研究物质的电子结构、电子关联效应和电离机制的强有力手段,其应用价值已经在物理、化学、生物等多个学科的发展和应用中得到了充分体现。目前,电子动量谱学的实验研究已经发展到高效率、高性能的第三代动量谱仪,可以开辟一些过去无法展开的新的研究领域和方向。本论文的内容主要包括单粒子格林函数方法在若干个分子的电子动量谱学研究中的应用和芯轨道动量分布的理论研究两部分。以二氧甲基甲烷和正戊烷分子为研究对象,结合焦点分析法(Focal Point Analysis)、单粒子格林函数和电子动量谱学系统地展开了分子构像问题的理论和实验研究。进一步验证了EMS在研究柔性分子的构像问题这个方向上的应用前景,并从轨道层次上观察到二氧甲基甲烷具有的端基异构效应和由正戊烷分子框架扭曲引起的轨道结构的变化。采用单粒子格林函数理论重新诠释了环状不饱和分子噻吩(C4H4S)和环戊烯(C5H8)的(e, 2e)电离能谱和动量谱实验数据,分析了轨道动量谱的实验和理论结果,证明了外价轨道和内价轨道的劈裂,弥补了OVGF,Hartree-Fock和DFT理论方法对(e, 2e)复杂过程表述的缺陷;发现了d-like分子轨道在低动量区有异常翘起的现象,显示出在电子电离过程中发生的原子核运动引起的vibroninc coupling也有可能是产生这种“上翘”现象的原因之一,在这种情况下Born-Oppenheimer-平面波冲量近似模型无法正确描述实验测量结果;对比结果让我们在动量空间中观察到轨道电子间的亚甲基σ-hyperconjugation超共轭相互作用。对含有等价同元素原子的分子芯轨道开展了电子动量谱学理论研究。由于等价原子轨道间的干涉作用,动量空间中轨道电子密度的分布表现为周期性振荡变化的曲线,通过它可以获得分子的几何结构和取向信息。更多还原

【Abstract】 Electron momentum spectroscopy (EMS), which can give both of the electron binding energies and the electron momentum density distributions at the same time, has been developed to be a powerful tool for the investigation of electronic structures, electronic correlation effects and electron ionization mechanics. It has extensive applications in the fields of physics, chemistry and biology. With the newly constructed third generation electron momentum spectrometer, which features high efficiency and high resolution, some new and valuable studies, which were very difficult in past, now become possible.This thesis mainly includes two parts: one is the interpretion of electron momentum spectra of valence molecular orbitals using one particle Green’s function method (1p-GF), the other is the investigation of electron density distribution in momentum space for core shells of molecules containing two equivalent atoms.The conformations of dimethoxymethane and n-pentane have been probed with Focal Point Analysis, one particle Green’s function and EMS. It has been exhibited that EMS has unexploited potential in experimentally studying conformation of versatile molecule, can image anomeric effects in dimethoxymethane, distortions and topological changes that molecular orbitals undergo under internal rotations and variations of forms of n-pentane in momentum space.Exhaustive EMS studies on thiophene and cyclopentene have been carried out with one particle Green’s function. Comparison between theoretical electron momentum distributions and experimental results confirms that outer and inner valence orbitals of two unsaturated ring molecules are both subject to breakdown of one electron picture of ionization, shows that, besides distortion effects, vibronic coupling probably results in the difference between experimental data and theoretical predictions at low momentum region in d-like orbitals, which are beyond Born-Oppenheimer plane wave impulse approximation, and moreover images through spaceσ-conjugations electronic interaction.The investigation of core states having two equivalent atoms have been presented. The momentum density maps of these core molecular orbitals exhibit periodical oscillation due to the interference effects of the equivalent atoms. Therefore, EMS can provide direct information on the nature of the nuclei geometry and orientation by investigating core states.更多还原