Electron spectroscopy using spin-selected metastable atoms

亚稳原子电子能谱是基于对稀有气体亚稳原子与固体表面热碰撞所发射的电子的分析。由于像He^&lt；**&gt；(1s2s，2^3s)这样的亚稳态原子不能穿透到块体中，局域化发生在最外表面。此外，电子发射是通过从亚稳态原子到固体表面的电子转移而发生的，因此电子转移速率本质上取决于表面波函数的空间分布。利用这些特征，我们用这种方法研究了过渡金属氧化物的电子结构，其中电子相关效应起着重要的作用。用He^&lt；**&gt；(1s2s，2^3s)研究LaCoO_3的电子发射谱表明，相对于O_2p衍生的带，下位的Co_3d衍生(主)带受到强烈的抑制，反映了初始Co_3d波函数的空间分布。另一方面，位于较高位置的Co3d(卫星)带在He^&lt；**&gt；谱中反常增强。基于Co2O11&gt；团簇的初始组态相互作用和最终组态相互作用，讨论了这些发现。

Metastable atom electron spewctroscopy is based on an analysis of electrons emitted by thermal collisions between rare-gas metastable atoms and solid surface. Since metastable atoms such as He^<**>(1s2s, 2^3S) can not penetrate into the bulk, the localionization takes place at the outermost surface layr. Further, the electron emission occurs through electron transfer from the metastable atom to solid surface, hence the transition rate is governed essentially by the spatial distribution of wave-function of the surface. Using these features, we have applied this method to probe the electronic structure of transition-metal oxides, in which the electron correlation effects plays an important role.The electron emission spectrum of LaCoO_3 using He^<**>(1s2s, 2^3S) shows that the lower-lying Co 3d-derived (main) bands are strongly suppressed relative to the O 2p-derived bands, reflecting the spatial distribution of the initial Co 3d wave-functions. On the other hand, the higher-lying Co 3d-derived (satellite) band is anomalously enhanced in the He^<**> spectrum. These findings are discussed on the basis of the initial and final configuration interactions, using Co_2O_<11> cluster.