Research on Electronic States in Clusters

该装置由两个真空室和一个差动泵浦系统组成，用来制作团簇，并测量束流中团簇的一些光学性质。样品的蒸发是在带有不同形状喷嘴的小铜瓶中用电子枪完成的。在另一个真空室中引入了小的团簇光束，在该真空室中安装了一对30 cm长的平行反射镜，用于测量光吸收、光散射和光发射等，该真空室也是收集团簇的装置。根据对银团簇束的初步实验结果，没有观察到等离子体吸收。测量了从冷却衬底中收集的CdSe团簇的光致发光的尺寸依赖关系。在大尺寸灌肠中观察到两条线，分别起源于激子和供体-受体对。然而，激发线的强度随着团簇尺寸的减小而减小，并且很难达到…在直径小于4 nm的团簇中观察到的更多。这一现象被解释为电子在团簇表面区的非弹性散射。小尺寸团簇的结构不是纤锌矿结构，而是锌混合结构。这可能源于表面积与体积之比的增大。用光声和发光光谱研究了光激发电子在硫化镉团簇中弛豫机制的尺寸依赖关系。非辐射复合速率随着团簇尺寸的减小而增大。其中一个成员通过采用红外吸收的二阶导数模式来研究氢化硅微晶薄膜。在薄膜中微晶颗粒的Si(111)和Si(110)面上分别在2100 cm~(-1)~(-1)附近出现了SiH的两个吸收峰，并成功地归属了SiH_2在Si(100)上和SiH_3在Si(111)和Si(110)表面上的对称和不对称伸展模式。此外，其中一位成员还从理论上研究了准晶的结构。发现了一种三维彭罗斯变换。线性尺寸的膨胀率和体积的膨胀率分别比人们所认为的要大得多。这种变换只唯一地决定了骨架，留下了其他一些不确定的自由度。它与确定性的二维情况有很大的不同。许多其他属性与2-D情况相同。这种转变有助于理解准晶结构。较少

The apparatus which was constructed from two vaccum rooms and a diffrerntial pumping system was bulided up to make a cluster veam and to measure some optical properties of clusters in the beam. Vaporization of sample was accomplished an electron gun in small Cu-botttle which had a various shaped nozzle. Small cluster beam was introduced into another vacuum room, in which a pair of 30cm-long parallel mirrors was settled for measurements of potical absorption, optical scattering and optical emission etc. This room also apparatus for collecting od clusters. According to result of preliminary experiment on Ag-cluster beam, the plasma absorption was not observed. The size dependence of photoluminescence of CdSe cluster which was gathered from a cooled substrate was measured. The two lines originating exciton and donor-acceptor pair, respectively, were observed in large size clysters. However, the intensity of excition line decreased with decreasing cluster size and the line could be hardly … More observed in cluster size less then 4nm in diameter. This phenomenon is interpreted to be due to the inelastic scattering of the electron in surface zone of cluster. The small size cluster had zincblend structure instead of wurtzite structure in bulk. It may originate from increase of the ratio of the surface to volume. Size dependences of relaxation mechanism of optically excited electrons in CdS clusters were also investigated by means of photoacoustic and Iuminescence spectroscopy. Non-radiative recombination rate increases with decreasing cluster size. One of the member has worked on hydrogenrated Si microcrystalline film by taking second derivative modes of infrared absorption. Two absorption peaks due to SiH on Si(111) and Si (110) surfaces of the mycrocrystalline grains in the film, respectively, near 2100 cm ^<-1> were clarified and the presence of both the symmetric and asymmetric modes of stretching in SiH_2 on Si(100) and SiH_3 on Si(111) and Si(110) surfaces was assigned successfully. Further, one of the member has studied theoretically on the structure of a quasi-crystal. A 3-D penrose transformation is found. The expansion rates <tau> in linear dimension and <tau>^9 in volume, are by far the larger than <tau> and <tau>^3 respectively ever believed. The transformation decides only the skeleton uniquely, leavin some other degrees of freedom undecicded. It strikinglydiffers from deterministic 2-D case. Many other properties are common with the 2-D case. This transformation is helpful in under standing the quasi-crystal structure. Less