气相电子衍射和SF_6分子中电荷再分布

GAS ELECTRON DIFFRACTION AND CHARGE REDISTRIBUTION IN SF_6 MOJECULE

气态小分子的电荷分布可从气相电子衍射实验得到。本文以SF_6分子为例作了研究讨论。我们引用Bonham等计算中性原子电荷密度分布和散射因子的参数法,提出了计算分子中原子的弹性散射因子的方法,利用这些不同于中性原子的散射因子,计算了折合散射强度,并和常规的理论计算结果相比较,两者的差别(残留强度曲线)主要反映分子形成后电荷再分布的影响。将它和实验中得到的残留曲线相比较,发现两者符合的程度,比用Hehre模型和用其他方法求得的结果好。文献[7]中存在的问题也作了讨论。

Independent atom model (IAM) is generaly used in gaseous electron diffraction (GED) experiment. This means that the effect of the charge redistribution in molecule is heglected in general case in GED data analysis and the information of the effect could be taken from the residual intensity.In this work, various methods were suggested to calculate the elastic scattering factors for S,F atoms in SF_6molecule (Modified IAM or MIAM) and the residual intensity of 40 kV electrons scattered by the same molecule.Bonham-type parameter method was selected to acheive good agreement with experimental results and the charge redistribution was determined according to these parameters.Further comparison was made between different methods and their results.A short disccusion was given concerning the reasons for the success and failure to fit the experimental data well for various methods.