【作者】 朱景升；

【导师】 邓景康；

【作者基本信息】 清华大学 ， 物理学， 2012， 博士

【摘要】 电子动量谱学（EMS）是研究原子分子中电子结构和碰撞动力学的强有力的工具，其独特优势在于能够同时测量轨道电子的结合能和电子的动量分布。利用高性能的第三代电子动量谱仪，可以深入挖掘过去未能发现的实验现象，结合相关理论研究，进而揭示这些现象背后深刻的物理规律。论文编写了新的高斯拟合程序，并作了详细说明。实验数据处理过程中关键的一步是用高斯拟合方法对能量-角度二维谱的剥谱处理。新程序使用方便可靠，大大降低了多高斯峰拟合的工作量。具有高对称性的小分子电子结构相对简单，轨道之间重叠较小，因而在理论和实验上更容易揭示现象背后的物理本质。论文的主要工作是利用高性能的第三代谱仪对若干小分子进行的电子动量谱学研究。我们成功地在不同实验条件下对I2分子进行了测量。对于外价轨道，自旋轨道相对论方法最好地描述了实验动量分布。相关轨道的动量谱以及分支比变化表明，相对论效应对I2分子价轨道动量分布的影响是不可忽略的。对于内价轨道，SAC-CI General-R方法在含相对论膺势的基组下的计算较好地模拟了复杂的伴线结构和相应的动量谱。采用截谱方法，发现了Jahn-Teller效应对NH3分子轨道动量分布的影响。简并的1e轨道中，具有更高结合能的区域在低动量区具有更高的强度。而非简并的3a1轨道则没有这种差别。相关振动模式下原子坐标位移对动量谱影响的分析可以定性地解释这种现象。对CF4、CCl4和CBr4分子中的扭曲波效应进行了系统的研究。三种分子的最高占据轨道都有很高的对称性和多个结面，在实验中都发现了扭曲波效应的特征：在低动量区，实验动量分布相对于理论分布“上翘”，且入射能量越高，翘起的程度越低。在其它两个轨道中也发现了扭曲波效应。此外，它们外价第5个轨道理论和实验符合得不好，并呈现出特定共同规律，目前其物理机制还不清楚。更多还原

【Abstract】 Electron Momentum Spectroscopy (EMS) is a powerful tool for investigating theelectronic structures and dynamics of electron scattering. It can measure the bindingenergy and the electron momentum distribution of each orbital simultaneously. With thehigh-performance3rdgeneration electron momentum spectrometer, we can explore thephenomena that can not be discovered in the past, and uncover the profound physicalmechanism behind those phenomena in cooperation with the theoretical study.A new Gaussian fitting program was compiled in the thesis for stripping the twodimensional energy-momentum spectra. The new program is robust and easy to use. Itgreatly reduces the complexity of Gaussian peak fitting.The highly symmetric small molecules usually have relatively simpleelectronic structures. As a result, it is easier to interpret the physical mechanismbehind the experimental phenomena. The main work of this thesis is toinvestigate a few small molecules using our high-performance EMSspectrometer.We successfully measured the I2molecule under different experimentalconditions. For the outer valence orbitals, the spin-orbit relativistic methodpresented the best descriptions for the experimental momentum distributions.The momentum spectra of related orbitals as well as the variation ofbranch-ratios manifest that the relativistic effect in I2can not be ignored. For theinner valence orbitals, the calculation using SAC-CI General-R method with thebasis set cooperating with the relativistic pseudo-potential can simulate thecomplicated satellites structures and their momentum distributions.The Jahn-Teller effect in the momentum distributions of NH3has beenobserved through comparing the distributions of the different slices. For thedegenerate1e orbital, the slice with a higher binding energy has a higherintensity in the low momentum region. This phenomenon has not been observedon the non-degenerate3a1orbital. It was found that the displacements of atomsunder different vibration modes can influence the momentum distributionsdifferently, which can qualitatively explain this phenomenon. We also systematically investigated the distorted wave effect (DWE) inCF4, CCl4, and CBr4molecules. The HOMOs of them are all highly symmetricwith many nodal planes, and the features of DWE have been observed in theexperimental momentum distribution: there is a turn-up in the low momentumregion, and experimental intensitiy decreases as the incident energy increases.The DWEs were also found in other two orbitals. Besides, in the5thorbitals ofthese molecules, a unique phenomenon was observed: the theoretical calculationdoes not well fit the experimental momentum distributions, and displays somecommon characteristics. The mechanism behind the phenomenon is still notclear.更多还原