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

根据晶体、液体和气体的状态，光学弛豫过程有很多种。这些过程可以简单地理解为电子-晶格相互作用的结果。但是，我们几乎不知道控制光学过程的主要物理常数。在这种情况下，我们只假设声子结构影响对凝聚态物质弛豫过程的影响。然后，我们试图捕捉什么样的声子激发剂的作用，以放松激发态的电子，特别是在非晶基质系统，如染料/聚乙烯醇。另一方面，由于四波混频可以检测出uv的阶数差异，是探测分子环境条件最通用、最灵敏的方法之一。首先，我们利用单色仪检测了在SiC热源的单色光调谐到OH伸展模式的振动能量的红外辐射下的相弛豫时间T2。在本例中，样品以磺胺640和PVA为基体，样品温度为4.2 K。在本实验中，我们无法检测到红外光打开或关闭时T2的变化。由于碳化硅源的强度很弱，很难对其进行定位，所以实验还没有完成。现在我们来做这个实验。接下来，我们利用Mira-OPO惰光作为激发红外光，其波长为2.7um，脉冲持续时间约为120 fs。在这种情况下，在惰光照射前，T2明显减少到原来的一半。但现在我们不能理解这是有意义的微热效应，因为样品温度可能只是简单地升高了。无论如何，我们现在正在继续进行更精确的实验。

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.