IR-Vis sum-frequency generation circular-dichroism studies on ultra-thin films of chiral molecules.

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We have investigated IR-Vis Sum-Frequencey-Generation Circular Dichroism of the ultra-thin films of chihalmolecules, which has been attracted considerable attention for biological and/or medical application. This technique may possibly provide 10^8 times more efficiency than those from any conventional techniques to study the chirarity of the molecules.We have reformed our old conventional ps-YAG laser and OPG/OPA system with LBO Crystal. We obtained IR laser beams by taking differential frequency of a fundamental YAG and the idler beam of OPA on a AgGaS_2 crystal. We have inserted a quater-wave plate into a visible beam to make left and right polarized light, and then mixed with the IR beam to obtain SFG-CD signal.The samples used in the experiment were ferro-and antiferro-electric liquid crystal molecules. We have successfully obtained SFG-CD signal for mono-molecular-layer thick samples. We have extended IV-SFG studies on the air/liquid interface structure of room temperature ionic liquids. In relation to this experiment, we have also performed the studies of molecular conformation by using near edge X-ray absorption fine structure spectroscopy.