Development of Two-Dimenssional Raman Spectroscopy Based on Seventh Order Optical Nonlinear Phenomena

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Two-dimensional Raman spectroscopy based on seventh order optical nonlinear phenomena has been developed experimentally and theoretically. We have constructed two short pulse laser system in order to perform the two-dimensional Raman experiment. One is a femtosecond dye laser system, which can produce two short pulses with different colors. The pulse width is about 100 fs. The other system is an intra-cavity dumped Ti : sapphire laser system, which produces a pulse width of 13 fs and energy of 67 nJ/pulse at 4 MHz. Currently, a multi-pass (six-pass) amplifier with a Ti : sapphire crystal is being designed and constructed to get a higher energy pulse. The purpose of this amplifier is to get a pulse with an energy more than sub microJ/pulse at 20 kHz. We are now constructing a detectionsystem inclusing optics for the seventh order nonlinear experiment. Theoretically, we have developed two different models to predict the two dimensional vibrational spectrum. One is to use perturbed states as stationary states and consider possible quantum pathways. By this method we show a physical picture ina qualitative level for the cross peaks in the seventh order two-dimensional Raman spectrum. The other method is to use unperturbed states as a basis set and solve a stochastic-Liouville equation. This method is capable of including more than two states in the formation quite easily, allowing us to apply optical nonlinear spectroscopy to dynamical studies of chemical reactions.