Singlet exciton relaxation in isolated polydiacetylene chains studied by subpicosecond pump-probe experiments
Singlet exciton relaxation in isolated polydiacetylene chains studied by subpicosecond pump-probe experiments
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DOI：
10.1103/physrevb.58.15777
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发表时间：
1998-12-15
影响因子：
3.7
通讯作者：
Schott, M
中科院分区：
文献类型：
--
作者：
Kraabel, B;Joffre, M;Schott, M
通过亚皮秒泵浦探针实验研究了在结晶单体基质中分离的聚二乙炔链中的单线态 B-1(u) 激子弛豫。介绍了光致吸收 (PA) 和 B-1(u) 激子吸收漂白 [光漂白 (PB)] 的结果。结果表明，除了三重体 B-3(u) 激子之外，光学间隙中还存在三个激发态。 PA 截面和 PB 效率非常相似的两个短寿命状态（各自的寿命 tau 大约为 450 fs 和 2 ps）属于相同的弛豫路径。第三个寿命较长的状态（tau 大于或等于 30 ps）负责缓慢的 PB 分量，并且独立于三线态激子而存在，三线态激子具有自己的特征 [B. Kraabel 等人，《化学》。物理。 227, 83 (1998)]。 B-1(u) 激子弛豫存在分支，不包括这三种状态的单个级联。所提出的非辐射弛豫方案涉及两种 Ag 状态。还讨论了自陷，得出的结论是，如果存在，它不可能是瞬时的。我们的数据表明，自捕获充其量只是聚二乙炔孤立链中 B1 单线态激子弛豫的次要组成部分。 [S0163-1829(98)02744-1]。
Singlet B-1(u) exciton relaxation in polydiacetylene chains isolated in their crystalline monomer matrix is studied by subpicosecond pump-probe experiments. Results on photoinduced absorption (PA) and on B-1(u) exciton absorption bleaching [photobleaching (PB)] are presented. It is shown that three excited states lie in the optical gap, apart from the tripler B-3(u) exciton. Two short-lived states (respective lifetimes tau approximate to 450 fs and 2 ps) of very similar PA cross sections and PB efficiencies, belong to the same relaxation pathway. A third longer-lived state (tau greater than or equal to 30 ps) is responsible for a slow PB component and exists independently of the triplet exciton, which has its own signature [B. Kraabel et al., Chem. Phys. 227, 83 (1998)]. There is a branching in the B-1(u) exciton relaxation, excluding a single cascade of these three states. The proposed nonradiative relaxation scheme involves two Ag states. Self-trapping is also discussed and it is concluded that, if present, it cannot be instantaneous. Our data suggest that self-trapping is at best a minor component of the B,, singlet exciton relaxation in polydiacetylene isolated chains. [S0163-1829(98)02744-1].