Terahertz Time-Domain Spectoscopy Of Base And Nucleosides

Terahertz electromagnetic wave has been attracted more attention recent years,Terahertz sources and terahertz time-domain spectra are two important fields in the terahertz technology.We have built up a terahertz time-domain spectral system based on the optical rectification and electro-optic sampling,and use it to investigate the absorption spectrum of the base and the nucleosides.Chapter one mainly introduced the basic conception,the unique properties and the characteristics of the terahertz electromagnetic wave.and we discussed the research actualities and the prospects briefly,we also descript the development process and the applications of the terahertz technology.Chapter two mainly introduced the methods and principles of the generation and the probe of terahertz radiation.it mainly has two commonly methods with the generation of the terahertz radiation:the photoconduction and the optical rectification.and the most commonly methods of the probing the terahertz radiation:the photoconduction sampling and the free space electro-optic sampling.In the end of this chapter,we emphasized the process of the experimental set up.here,we use the optical rectification to get the terahertz radiation and use the free space electro-optic to probe the terahertz radiation.Then we make a detailed statement of the experimental operation and got the signal of THz radiation experimentally measured.Chapter three introduced the theoretical model which associated with the whole process of the experiment.including the Fourier transtorm in the data processing.and we introduced the theoretical analysis about the optical rectification and the free space electro-optic sampling.also introduced the theoretical model of the Density Functional Theory which was used for the calculation of the molecular dynamics and the theory of the vibration frequency.Chapter four describes the application of the terahertz time domain spectroscopy in this experiment. describes the theoretical analysis of parameter extraction. and analyse the absorption of the cytosine, the cytidine and the uracil by the terahertz time domain spectrum. Their vibrational-rotational spectra in terahertz region have also been calculated and analyzed base on the theoretical calculations such as the B3LYP density functional method.we have analysised the absorption of the three molecules in the terahertz radiation, and found the answer: besides the absorption of the molecules themselves and the interference of the water vapor. there has the absorption of the molecular dimer, molecular trimer, tetramer, and even polymers.Chapter five is a summary of the contents of this articla, and prospects for the future work.