基于结构计算的分子动力学参数和共振态研究

发布时间：2018-04-10 11:41

本文选题：结构计算 + 多参考组态相互作用　；参考：《中国科学技术大学》2017年博士论文

【摘要】：随着先进光源技术进步,原子分子物理实验和理论研究都取得了快速发展。例如,基于第三代同步辐射技术发展的X射线散射方法,可以精确测量出原子动力学参数;利用自由电子激光技术,可以在飞秒甚至更快的时间尺度上对原子分子动力学过程进行调控。前者可以提供精确的形状因子平方(Squared Form Factor,SFF),该参数可以很好地表征原子分子基态和激发态波函数在不同空间尺度区域的行为;后者可以用于研究原子分子亚稳态的动力学行为,并且新发现了诸如原子间库伦衰变(interatomic coloumb decay,ICD)这种有趣的现象。原则上,一阶Born近似下原子分子动力学参数的计算精度,仅仅取决于结构计算的精度。以往的实验证明,X射线和原子体系(He、Ne、Ar)的散射中,一阶Born近似成立。然而对于X射线和分子体系的散射,一阶Born近似的成立情况尚不清楚。同时,基于玻恩-奥本海默近似计算的分子结构精度,也有待进一步的检验。因此,有必要开展X射线和分子的散射实验,以及相关的理论计算,来验证一阶Born近似的成立性,并评估分子结构计算方法的精确度。对于共振态,由于其波函数具有一定的局域特性,可以采用一些特殊手段,利用束缚态计算方法进行研究。分子结构的计算方法众多,在本文中采用基于变分原理的"多参考单双激发的组态相互作用方法(multi-reference single and double excitation configuration interaction,MRSDCI/MRCI)"来计算束缚态的结构,并将该方法拓展至复数区域,结合复坐标旋转方法(complex coordinate rotation method,CRM)以及复吸收势法(complex absorption potential,CAP),用于原子分子的共振态以及ICD态的计算。本论文的具体工作如下:(1)采用MRCI方法计算了 H_2以及N_2的电子态结构,并结合一阶Born近似计算了相应的弹性以及非弹性的动力学结构参数,同时采用非弹性X射线散射方法测量了 N_2在12-13.3eV激发能区振动分辨的动力学参数。对于简单的体系H_2,非相对论的渐进能量计算精度很高,且动力学参数的计算结果和X射线散射实验结果符合很好。对于较复杂的体系N_2,动力学参数的计算结果和实验结果也符合很好,同时发现对于部分态,中能和高能电子能量损失谱方法未能达到一阶Born近似。以上结果成功证实了 X射线和分子体系散射中一阶Born近似的成立性,拓展了X射线散射方法作为实验基准数据的评估范围。另一方面,H_2动力学参数的计算结果和X射线散射实验结果的差异似乎较为反常,其背后可能有值得考虑的物理机制;(2)发展了计算一维分子振转共振态的CRM/CAP+DVR方法,可以精确计算双原子分子振转亚稳态的共振能级和自解离速率。利用该方法计算了 Cu_2和LiH~-分子的振转自解离态,对于CU_2~-的解离速率,采用CRM+DVR方法计算的结果和使用WKB近似计算的结果差别了近一个数量级,说明WKB近似对于大质量的粒子并不适用。LiH-共振能级和宽度的计算结果和分子轨道强耦合方法(QMOCC)的计算结果符合很好,两种方法互相验证了可靠性,而本文的CAP+DVR方法同时还可以辅助标注各个共振峰对应的振转态的量子数;(3)成功实现以CRM+MRCI方法计算原子分子Feshbach共振态。通过计算Nq+(q=2-5)离子的k壳层空穴态的共振参数,摸索出合适的基组选择方法,得出了 28个共振Auger态的能级和宽度数据,计算结果与其他理论和实验值符合很好,并验证了与自旋相关的Auger速率关系。成功计算了He_2~+的ICD态宽度,相对于其他方法,本文的CRM+MRCI方法采用更小的基组和计算量,获得精度相当的计算结果。
[Abstract]:With the advanced light source technology, atomic and molecular physics experiments and theoretical research have achieved rapid development. For example, X ray scattering method of third generation synchrotron radiation based on the development of technology, can accurately measure the atomic dynamics parameters; using free electron laser technology, can even femtosecond faster time scales of atomic and molecular dynamics in the process of regulation. The former can provide accurate square shape factor (Squared Form, Factor, SFF), the parameters can be well characterized molecular and atomic ground state excited state wave function at different spatial scales in the area of behavior; the latter can be used to study the dynamics of metastable atoms and molecules, and the newly discovered atoms such as Kulun decay (interatomic Coloumb decay, ICD) this interesting phenomenon. In principle, calculation of the first order Born approximation in atomic and molecular dynamics parameters of precision, simply In the structure calculation accuracy. The experiment proved that, X rays and atomic system (He, Ne, Ar) scattering in the first order Born approximation is established. However, for X ray scattering and molecular system, the establishment of the first order Born approximation is not clear. At the same time, Born - Oppenheimer in the molecular structure of precision based on calculation, also needs to be further tested. Therefore, it is necessary to carry out X X-ray scattering experiments and molecular computation, and the related theories, to verify the validity of the first order Born approximation, and the calculation method of molecular structure accuracy. For resonance due to the wave function with local characteristics, we can use some special means, use bound calculation methods were studied. Many calculation methods of molecular structure, the multireference single and double excitation configuration interaction method based on the variational principle "in this paper (multi-reference single and Dou Ble excitation configuration interaction, MRSDCI/MRCI) "to calculate the structure of the bound state, and this method is extended to complex area, combined with the complex coordinate rotation method (complex coordinate rotation method, CRM) and the complex absorption potential (complex absorption potential, CAP method), used in atomic and molecular resonances and calculation of ICD state. The specific work this paper is as follows: (1) using MRCI H_2 method and electronic structure of N_2 is calculated, and combined with the first-order Born corresponding elastic and inelastic dynamic structural parameters were calculated using non elastic approximation and X ray scattering method N_2 kinetic parameters of vibration excitation in 12-13.3eV resolution measurement system for H_2. Simple, non relativistic asymptotic energy has very high calculation precision, calculation results and kinetic parameters of X and X-ray scattering is consistent with the experimental results. For more complex body. Department of N_2, the calculation results of kinetic parameters and experimental results are in good agreement, also found that for part of the state, and in high energy electron energy loss spectroscopy method can meet the first order Born approximation. The above results confirmed the successful establishment of the first order Born approximation in X ray system and molecular scattering, extended X ray scattering method as the experimental reference data to assess the scope. On the other hand, the difference calculation results of kinetic parameters of H_2 and X ray scattering of experimental results is likely to be abnormal, which might be behind a physical mechanism worthy of consideration; (2) the development of the CRM/CAP+DVR method in the calculation of one-dimensional molecular vibrational resonances. The resonance level can be accurately calculated for diatomic molecules rovibrational metastable and self dissociation rate. Cu_2 and LiH~- molecular rovibrational self dissociation is calculated by using the method, the dissociation rate of CU_2~-, and the results calculated by CRM+DVR method Using the WKB approximate calculation results differ by nearly an order of magnitude, indicating that WKB approximate calculation results for large mass particles is not suitable for.LiH- and the width of the resonance level and the molecular orbital coupling method (QMOCC) calculation results are in good agreement with each other, the two methods to verify the reliability of the CAP+DVR method in this paper, and at the same time you can also assist marked quantum number of each resonance peak corresponds to the rovibrational states; (3) the successful implementation of the CRM+MRCI method in the calculation of atomic and molecular resonances. Through the calculation of Nq+ Feshbach (q=2-5) k resonance parameters of shell holes ions, find out suitable basis set selection method, the level and width of data 28 Auger resonance state, the calculated results are compared with other theoretical and experimental values are in good agreement, and verify the Auger rate relationship with spin dependent. The success of the He_2~+ ICD state width was calculated and compared with other methods, this paper CRM+MRCI The method uses the smaller base group and the amount of calculation to obtain the accurate calculation results.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O561

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