Real-time observation of motion and shape of the wave-packet during ultrafast lattice relaxation

利用上转换技术，可以观察到飞秒时间分辨率的红外发光。本项目的目的是通过提高发光测量的时间分辨率来观察波包包络在飞秒时间尺度上的时间演化。通过激发电荷转移吸收带，研究了准一维卤素桥联铂配合物中自陷态激子的产生和衰变过程。我们观察到了不同能量下发光强度随时间演化的特征振荡。项目开始前的时间分辨率被提高到50飞秒，这几乎是世界最好的记录，我们能够获得非常清晰的数据。在诸如瞬时吸收等普通的飞秒测量中，由于观测到的是绝热电势在小范围内的时间响应，因此不可能反演出波包的时间发展。然而，发光方法使我们能够在绝热势面上的许多不同点获得更多的时间信息。通过对基于模型计算的实验数据的分析，我们成功地反演了随时间变化的波包包络。结果表明，波包的空间宽度在1/2周期时增大到初值的2.5倍，在一个周期内增大到3倍。

It is possible to observing infrared luminescence with a femtosecond time resolution, using up-conversion technique. The aim of this project is to observe time evolution of the wave-packet envelope in femtosecond time scale by improving the time resolution of the luminescence measurement. We investigated the generation and decay processes of the self-trapped excitons in the quasi-one-dimensional halogen-bridged platinum complexes by exciting the charge transfer absorption band. We observed characteristic oscillation in the time evolution of luminescence intensity at various energies. The time resolution before starting the project was improved to 50 fs, which is nearly the world best record and we were able to obtain very clear data. In the ordinary femotosecond measurements such as transient absorption, it is impossible to retrieve the time development of the wave-packet envelope, because the time response in a small range on the adiabatic potential is observed. However, the luminescence method allows us to get much more temporal information at many different points on the adiabatic potential surface. From the analysis of the experimental data based on a model calculation, we successfully retrieved the time dependent wave-packet envelope. The result shows that the spatial width of the wave-packet increases to 2.5 times of the initial value at 1/2 period and 3 times at one period of oscillation.