Study of characteristic role of lower lying energy levels in optical relaxation processes

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There are many kinds of optical relaxation processes according to the states of crystals, liquids and gasses. These processes are understood as the results of electron-lattice interaction briefly. But, we do not almost know main physical constants to control the optical processes. In that case we only suppose phonon structures affecting the influences to the relaxation processes in condensed matters.Then we have attempted to catch what kinds of phonon making role of activator to relax the excited electron states, in particular, in the system of amorphous matrix such as dye/polyvinylalcohol. On the other hand, four-wave mixing is one of the most versatile and sensitive methods to detect the environmental condition of the probe molecular since it can detect the difference of the order of ueV.At first, we have performed to detect the phase relaxation time T2 under irradiating IR radiation which was monochrolized light tuned to the vibrational energy of OH stretching mode from SiC thermal source by using monochrometor. In this case, sample was sulfurohdamine 640 and PVA as matrix and the sample temperature was 4.2 K. In this experiment, we have not been able to detect the change of T2 when the IR light was on or off. This experiment has been not so complete because the intensity of SiC source was so weak that alignment was very difficult. Now we attempting this experiment.Next, we employed Mira-OPO idler light as an exciting IR light whose wavelength was 2.7um and pulse duration was about 120 fs. In this case, T2 was clearly reduced into the half of it before irradiating idler light. But now we can not understand that this is meaningful micro-thermal effect because sample temperature might have raised simply.Anyway, we are now continuing the more precise experiment.