Femtosecond transient absorption spectroscopy of nanocrystalline polydiacetylene colloids
Femtosecond transient absorption spectroscopy of nanocrystalline polydiacetylene colloids
复制标题
纳米晶聚二乙炔胶体的飞秒瞬态吸收光谱
DOI：
10.1080/10587259808042462
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
H. Nakanishi
中科院分区：
文献类型：
--
作者：
T. Asahi;Kazumasa Kibisako;H. Masuhara;H. Kasai;H. Katagi;H. Oikawa;H. Nakanishi
对分散在水中的尺寸可控的聚二乙炔微晶(平均直径分别为30、100和150 nm)进行了飞秒瞬时吸收光谱测量。激发后5ps内的超快弛豫过程归因于自陷态激子的形成和衰变，该过程与激子大小无关。在10ps到几ns的时间范围内，观察到与稳定激子吸收带相对应的瞬时漂白光谱随时间的漂移。通过比较微晶的瞬时吸收光谱和基态吸收的温差光谱，将其解释为微晶内吸收光能的热化和随后的冷却。成功地证明了“热”微晶的尺寸相关冷却动力学，时间常数随晶体尺寸的增大而增大。
Abstract Femtosecond transient absorption spectral measurements have been performed for size-controlled polydiacetylene microcrystals (30, 100, and 150 nm mean diameter) dispersed in water. Ultrafast relaxation processes within 5 ps after excitation were attributed to formation and decay of self-trapped exciton, which was independent on the size. A time-dependent spectral shift of transient bleaching, corresponding to the stationary excitonic absorption band, was observed in the time region from 10 ps to a few ns. It is explained as a thermalization of absorbed light energy within the microcrystal and the succeeding cooling by comparing transient absorption spectra with temperature difference spectra of the ground state absorption. Size-dependent cooling dynamics of a “hot” microcrystal was successfully demonstrated; the time constant increases with the crystal size.