ELECTRON SPECTROSCOPIC STUDY ON ELECTRONIC STRUCTURES DEPENDENCE ON FULLERENE NETWORKS

人们认为存在一种叫做Carbyne的线性碳链材料，但由于其不稳定性，其性质尚未得到很好的研究。Carbyne由两种类型的化合物组成，即culculene型和polyyne型。为了研究碳炔的电子结构，测量了碳炔模型化合物的光电子能谱。本文用分子轨道（MO）计算方法估计了由于合成困难而无法测量光电子能谱的线性碳链化合物的电子结构。用MO计算可以很好地解释光电子能谱。累积烯类和聚炔类化合物的最高占据分子轨道（HOMO）都位于线性碳链上，而不是为稳定分子而引入的端基上。HOMO的结合能（电离能）随链长增加而减小。结果表明，当碳原子数相同时，堆积烯型化合物的HOMO能级和生成热均大于聚烯烃型化合物。测定了钙原子包封富勒烯、Ca@C82两种异构体的光电子能谱。光谱表现出与其他富勒烯相同的振荡强度。从头算出了它们可能的结构。从钙原子转移到富勒烯笼的电子数量估计为2。对单壁碳纳米管和C60封装管进行了光电子发射测量，但尚未获得可靠的数据。这些尝试正在进行中。

An existence of linear carbon chain materials called Carbyne has been suggested, but their nature has not been investigated well because of its instability. Carbyne consists of two types compounds called cumulene type and polyyne type. In order to investigate the electronic structures of carbyne, photoelectron spectra of carbyne model compounds have been measured. Molecular orbital (MO) calculation has been performed to estimate the electronic structures of the linear carbon chain compounds of which photoelectron spectra could not be measured because of difficulty of their synthesis.The photoelectron spectra could be interpreted very well with the MO calculation. The highest occupied molecular orbital (HOMO) of both cumulene and polyyne types compounds resides on the linear carbon chain, not on the termination groups that were introduced to stabilize the molecules. The binding energy (ionization potential) of the HOMO decreases as the chain length increases. It was found that when the number of carbon atoms is the same the HOMO level and the heat of formation of cumulene type compounds are larger than those of polyyene type ones.Photoelectron spectra of calcium atom encapsulated fullerenes, two Ca@C82 isomers were measured. The spectra showed intensity oscillation as those of other fullerenes. ab initio calculation suggests their possible structure. The amounts of transferred electrons from the calcium atom to the fullerene cage was estimated to be two.Photoelectron emission measurements from single wall carbon nano tubes and C60 encapsulated tubes were tried, but reliable data have not been obtained yet. The attempts are under the way.