Experimental Study on Creation and Decay Processes of Excitons in Rare Gas Clusters

在本项目期间，我们设计建造了用电子能量损失谱研究稀有气体团簇中电子激发过程的装置，并对Kr团簇中的激子激发过程取得了一些初步的结果。实验装置包括真空室，包括抽运系统、电子能量损失谱、两种超音速团簇束源和用于测量团簇尺寸分布的团簇离子探测器。利用差动低温抽运的团簇束源，我们测量了在100 eV电子碰撞能量和0°观察角下，Kr_n团簇(n=500-600)的电子能量损失谱。我们已经清楚地观察到了团簇中与孤立原子中4p^55s态激发相对应的表面激发子的产生。我们从明年开始的计划如下：(1)用最近建立的常规型团簇束源测量Ne和Ar团簇的激子激发光谱。(2)证实了稳定的负电荷Kr和Xe团簇的存在，它们的电子亲和势在原子中为负，在固体中为正，这表明团簇中电子亲和力的符号发生了变化。

During the term of this project, we have designed and constructed and apparatus for the study of the electronic excitation processes in rare-gas clusters using the electron energy loss spectroscopy, and have obtained some preliminary results for the excitonic excitation process in Kr cluster. The experimental setup consists of a vacuum chamber including a pumping system, an electron energy loss spectrometer, 2 types of supersonic cluster beam source, and a cluster ion detector for the measurement of the cluster size distribution.Using the cluster beam source using a differential cryo pumping system, we have measured the electron energy loss spectra for Kr_n cluster (n=500-600), at the electron impact energy of 100eV and the observation angle of 0 deg. Creation of the surface excition in the cluster, which corresponds to the excitation of 4p^55s state in an isolated atom, has been clearly observed.Our plan from the next year is as follows,(1) Measurement of the excitonic excitation spectra for Ne and Ar clusters using a conventional type cluster beam source, which has been constructed recently.(2) Confirmation of the existence of stable negatively charged Kr and Xe clusters, whose electron affinities are known to be negative in atoms, and positive in solids, which suggests the change of the sign of electron affinity in clusters.