Electron spectroscopy using spin-selected metastable atoms

亚稳态原子电子光谱是基于对稀有气体亚稳态原子与固体表面热碰撞所发射的电子的分析。由于He^<**>(152s, 2^3S)等亚稳原子不能穿透到体中，所以定域发生在最外层。此外，电子发射是通过电子从亚稳原子向固体表面的转移而发生的，因此跃迁速率本质上是由表面波函数的空间分布决定的。利用这些特征，我们将该方法应用于过渡金属氧化物的电子结构探测，其中电子相关效应起着重要作用。He^<**>(152s, 2^3S)对LaCoO_3的电子发射谱图进行了分析，结果表明，相对于O ^ 2p衍生的电子发射谱，较低的Co - 3d衍生（主）谱带被强烈抑制，反映了初始Co - 3d波函数的空间分布。另一方面，高海拔Co 3d衍生（卫星）波段在He^<**>光谱中异常增强。这些发现是在Co_2O_<11>簇的初始和最终构型相互作用的基础上进行讨论的。

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.