The geometry relaxation and intersystem crossing of quaterthiophene studied by femtosecond spectroscopy
The geometry relaxation and intersystem crossing of quaterthiophene studied by femtosecond spectroscopy
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DOI：
10.1039/c4pp00439f
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发表时间：
2015-04
影响因子：
3.1
通讯作者：
Si-mei Sun;Song Zhang;Kai Liu;Ya-ping Wang;Bing Zhang
中科院分区：
文献类型：
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作者：
Si-mei Sun;Song Zhang;Kai Liu;Ya-ping Wang;Bing Zhang
四噻吩是一种生物荧光标记物，但由于分子结构的复杂性和能级顺序的不确定性，其高三重态生成率的内在激发态动力学仍存在争议。本文采用飞秒时间分辨光谱结合量子计算方法研究了四噻吩分子在1，4-二氧六环中的超快几何弛豫和系间跃迁。在泵浦波长为400 nm的瞬态吸收光谱被完全记录到1 ns的延迟时间。激发态吸收的动力学曲线表明，在S_1势能面上发生了几何弛豫，时间常数为1.70 ps。两个三重态-三重态吸收带分别位于563 nm和600 nm处，显示出直接的动力学转换。系统间的穿越被确定为398 ps。通过有效的系间交叉，测得高三重态产率为10.7。在量子化学计算的基础上，提出了一个描述几何弛豫和系间交叉过程的一般机制。
Quaterthiophene is used as a fluorescent marker for biological applications, but the intrinsic excited state dynamics for its high triplet-formation yield are still under debate due to the complexity of the molecule structure and the undetermined energy level order. In this work, ultrafast geometry relaxation and intersystem crossing of quaterthiophene in 1,4-dioxane are studied by femtosecond time-resolved spectroscopy combined with quantum calculations. Transient absorption spectra at a pump wavelength of 400 nm are completely recorded up to the delay time of 1 ns. The kinetic traces of excited state absorption indicate that geometry relaxation occurs on the S_1 potential energy surface with a time constant of ∼70 ps. Two triplet–triplet absorption bands centered at 563 nm and 600 nm show a direct dynamical conversion. The intersystem crossing is determined to be ∼398 ps. The high triplet yield is measured as ∼0.7 via the efficient intersystem crossing. On the basis of quantum chemical calculations, a general mechanism is proposed to describe the geometry relaxation and intersystem crossing processes.