Study About The Biological Molecular Of Two-dimension Third-order Nonlinear Laser Spectrum

This paper mainly introduces two different theory structures to simulate two-dimensional third-order nonlinear electronic spectroscopy.Chapter one, we introduce the fundamental knowledge about the two-dimensional electronic spectroscopy, mainly includes the time evolution operator, response function and correlation function. Time evolution operator could derive the nth-order response function. The correlation function carries all the necessary microscopic information.Chapter two, we derive the expression of third-order nonlinear response function by the cumulant expansion method. At the same time, we also introduce the hierarchical equation of motion method---an accurate numerical simulation method. Then we use the cumulant expansion method and hierarchical equation of motion method to do the numerical simulation for two-dimensional electronic spectra, we can find that use the cumulant expansion approach, the response function with different linear functions will lead to different spectra results. But if we use response function with non-markovian linear function to simulate the spectra, the result is the same with the hierarchical equation of motion. It means that the cumulant expansion method is an accurate approach.Chapter three, we introduce a new method to simulate the two-dimensional electronic spectra(time-nonlocal method with the equation-of-motion phase matching approach), it is a special way that this theory method needn’t calculate the response function. Because the high order dissipative term of time-nonlocal method’s expression is neglected. In order to judge the precision of time-nonlocal method, we compare this method with hierarchical equation of motion. The result about the time evolution of density matrix is similar. It turns out that the time-nonlocal method is accurate. Then we use time-nonlocal method to simulate the energy transfer process of the complex which can conduct the photosynthesis. The result is satisfactory.Chapter four, summarized the three methods in this paper. The outlook on simulating the photosynthesis systems with these methods.