蓝宝石的近边精细结构和电子数布居分析

ANALYSIS OF NEAR EDGE FINE STRUCTURE AND ELECTRONIC POPULATIONS IN SAPPHIRE

利用透射电子显微镜的电子能量损失谱研究了蓝宝石ＡｌＬ和ＯＫ近边精细结构，给出了Ａｌ原子和Ｏ原子的电子数布居分析及不同分截面的比较．通过考虑一个原子在均匀固体中的电离来解释近边电离区中的元素效应．应用推广的Ｈüｃｋｅｌ分子轨道理论及反映了晶体变换对称性影响的布洛赫定理来计算电子从内层向价层的跃迁，从而解释了近边区域的化学效应．还考虑了附加的化学效应，这来自激发原子附近的原子产生的外行平面波弹性后向散射，由此产生电离区中的所谓延展精细结构．

AbstractAlL and OK near edge fine structures in sapphire are studied using electron energy loss microspectroscopy in a transmission electron microscope;an analysis of the electronic populations of atoms Al and O,and a comparison between different partial cross sections are given.We consider the ionization of an atom in a homogeneous solid to interpret the elemental effects in the ionization region near edges.The chemical effects in the region near edge onset are interpreted by using extended Hückel molecular orbital theory and Bloch's theorem including the effects of translation symmetry in crystals to calculate the electronic transitions from core shell to unoccupied valence shell.We also consider the additional chemical effects, which arise from the elastic backscattering of the atomic ionization waves by the atoms neighboring the exited atom,giving rise to the so called extended fine structure in the ionization region.The agreement between the calculated results and the experimental energy loss spectra of sapphire from single phase region is good.