咔唑分子拉曼激发虚态的相关研究

根据键极化率与拉曼峰强之间的关系,得到咔唑分子拉曼激发虚态随时间演化的键极化率. 将得到的键极化率的末态与用密度泛函理论得到的基态键电荷密度进行了对比,讨论并分析了拉曼激发虚态键极化率随时间弛豫的特征. 研究表明:咔唑分子在拉曼激发初态时,电子由两个骨架六元环向连通两六元环的连通键上流动,而并非向外围的C–H键上流动. 拉曼激发末态键极化率分布趋势与基态键电荷密度分布很相似,说明激发的电子又流回到分子骨架,即弛豫到基态. 通过对拉曼激发虚态键极化率弛豫过程特征时间的研究,发现连通两六元环的C–C键以及靠近连通键的C–C键的键极化率的弛豫时间较其他键的极化率弛豫时间都长,进一步说明了拉曼激发虚态电子弛豫特征. 这些结果反映了咔唑这类具有连通键的多元环分子在拉曼激发虚态所具有的特征与性质,这对拉曼激发虚态的研究有重要意义.关键词：拉曼峰强键极化率拉曼激发虚态

The study of nonresonant Raman excited virtual state of carbazole molecule

According to the relationship between Raman intensity and the bond polarizability, we investigate the temporal bond polarizabilities of carbazole molecule from the Raman intensities. We obtain the bond polarizability of the final state and compare it with the electronic density of the ground state by the density functional theory method, then we discuss and analyze the characteristics of carbazole temporal bond polarizabilities. The results show that at the initial stage of exitation, the excited electrons tend to flow toward the bond that we called connecting bond, which connects the two six-member ring, but not toward the molecular periphery. The bond electronic density of the molecule ground state can be mapped out by the temporal bond polarizabilities at the final stage of relaxation, therefore we conclude that the excited electrons flow back to the skeleton bond. Furthermore, we find the relaxation characteristic time of connecting the bonds is longer than that of connecting the other bonds, this further confirms our observations mentioned above. These conclusions will improve our understanding of Raman excited virtual states of the molecule with the bridge bonds.