New Spectroscopy using combination of synchrotron radiation and laser

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In order to investigate the photo-induced phase transitions, we have been developing new techniques based on the combination of synchrotron radiation and laser in recent years.(1) We have constructed the new fast data acquisition system at the XAFS station of KEK-PF, where intense X-rays from a wiggler can be used. The system is powerful to investigate the photo-induced structural change since XAFS can provide the local atomic distance between the constituents. The system was applied to a spin crossover complex, resulting in the new information of the crystal structure of photo-induced phase.(2) We have also constructed the combination photoelectron system based on the synchrotron radiation and laser at UVSOR, Institute for Molecular Science. AT beam lines BL5A and BL6A2, core-level photoelectron spectroscopy was carried out to investigate the photo-induced surface photo voltage on GaAs. The photo-induced phase transition on a single crystal of [Fe(2-pic)_3] Cl_2EtOH. was also investigated with photoelectron spectroscopy using synchrotron radiation and laser. The UPS spectra of valence states of Fe(2-pic)_3] Cl_2EtOH did not show any change by laser excitation at room temperture, but it showed clearly that the valence states drastically changed by cooling the sample from RT to 40K and also by the laser-excitation at 40K. The experimental results indicate that the electronic structure of the photo-induced phase is not the same as that of the high-spin state.(3) At Kyoto university single crystals of spin crossover complexes were grown and the ESR and Raman systems were constructed to investigate the photo-induced phase transition. The Raman spectroscopy results indicated the clear evidence of the symmetry lowering in the photo-induced phase of [Fe(2-pic)_3] Cl_2EtOH.(4) AT Saga University, the future prospect of the combinational use of synchrotron radiation and laser for photo-induced phenomena was discussed.