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Dissertation for the Master Degree in Science
Two-dimensional Femtosecond Laser Electronic Spectra of a Dimer System
Candidate:
Wang Zanhao
Supervisor:
Prof. Yang Yanqiang
Academic Degree Applied for:
Master of Science
Speciality:
Condensed Matter Physics
Affiliation:
Department of Physics
Date of Defence:
June, 2011
Degree-Conferring-Institution:
Harbin Institute of Technology
摘要
近几年,光谱研究技术从传统的一维光谱向二维或三维光谱方向迅速发展, 如红外、拉曼、荧光等二维光谱等,它们相对于一维光谱来说,以较高的分辨率和能够清楚的辨明材料分子内各基团的相互关系,在很多研究领域得到了广泛的发展和应用。随着实验技术及飞秒激光的迅速发展,飞秒激光二维电子光谱,在飞秒时间分辨率下研究材料内的电子态信息,也正引起学者浓厚的兴趣。飞秒二维电子光谱是在时域中分子体系由一系列超快飞秒激光脉冲作用下所产生的受激振动光子回波响应,再经过二维傅里叶变换后在二维频域中的表示。
本课题重新推导了二维电子光谱的理论表达式,利用累积量展开及稳相法等得到了二维光谱的解析表达式,并分析了表达式中各参数的物理意义。利用 Frenkel 激子模型构造了二聚体体系的能级结构,并利用二维电子光谱的解析表达式及对应的双边费曼图,得到了相位重构和非相位重构二维电子光谱的解析表达式,进而得出完整的二维电子光谱。
利用 MATLAB 软件,对相位重构及非相位重构二维电子光谱表达式进行了编程, 得到了欧姆型热库作用下完整的二维电子光谱弛豫光谱。分析了二维电子光谱的组成,对弛豫光谱中出现的量子拍进行了探讨,同时探讨了相位重构及非相位重构图像对对角峰及交叉峰出现的量子拍的贡献,从理论表达式分析得出相位重构只对交叉峰的量子拍有贡献,而非相位重构只对对角峰的量子拍存在贡献。
关键词:二维电子光谱;二聚体;响应函数;光谱密度
Abstract
Recently, spectroscopy technology has developed rapidly from the traditional one-dimensional spectroscopy to two- or three-dimensional spectroscopy, such as two- dimensional infrared, Raman, and fluorescence spectroscopy. These technologies have been developed and applied frequently due to their abilities to discriminate the relationship between different molecular groups with high resolution parison to the one-dimensional spectroscopy. With the development of relevant experimental techniques and femtosecond lasers, two-dimensional femtosecond laser electronic spectroscopy has attracted great attention for it gives informations of electronic states in materials with femtosecond resolution. Two-dimensional femtosecond laser electronic spectroscopy is a representation of the stimulated photon echo through the two-dimensional Fourier transform in frequency domain,which is generated by a series of ultrafast femtosecond laser pulses in