Optical Properties of Single-Wall Carbon Nanotubes

平均半径为0.55、0.65和1.0 nm的单壁纳米管的拉曼散射光谱显示，与石墨中的E&lt；2g&gt；模对应的光学声子峰随尺寸发生多次分裂。这些分裂构成了纳米管独特特征的第一个实验证据，即它们因其柱状对称性而表现出离散的和直径相关的分散。在石墨的基础上很好地解释了观察到的色散，并显示了在区域折叠方案中预测和控制纳米管基本性质的可能性。在450 nm到800 nm的入射激光波长下，测量了平均直径1.1 nm的单壁纳米管中光学声子的共振喇曼散射。散射强度在690 nm附近出现异常，纵向最小，横向最大。我们的光学透过率测量也显示出在相同的光子能量范围内的凹陷。这些反常现象是由入射激光与纳米管中的区域折叠电子结构共振引起的。这些结果构成了由纳米管的柱状对称性产生的STSTE密度临界点的直接实验证据。

Raman scattering spectra of single-wall nanotubes with mean radii 0.55,0.65 and 1.0 nm show size-dependent multiple splittings of the optical phonon peak corresponding to E_<2g> mode in graphite. These splittings constitute the first experimental evidence for the unique feature of nanotubes that they exhibit discrete and diameter-dependent dispersions arising from their cylindrical symmetry. The observed dispersion is well explained on the basis of graphite, and shows possibilities of predicting and controlling the basic property of nanotubes in the zone-folding scheme.Resonant Raman scattering from optical phonons in single-wall nanotubes of mean diamater 1.1 nm has been measured in the wavelength of incident laser beam between 450 nm and 800 nm. The scattering intensities exhibit anomalies in the vicinity of 690 nm, being a minimum in the longitudinal components and a maximum in the transverse. Our optical transmission measurement also exhibits a dip in the same photon energy range. The anomalies are caused by the incident laser beam resonant with the zone-folded electronic structures in nanotubes. These results constitute a direct experimental evidence of the critical point in the density of ststes produced by the cylindrical symmetry of nanotubes.