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

点击翻译按钮获取中文摘要

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.