Vibronic quantum effects in fluorescence and photochemistry. Competition between vibrational relaxation and photochemistry and consequences for photochemical control
Vibronic quantum effects in fluorescence and photochemistry. Competition between vibrational relaxation and photochemistry and consequences for photochemical control
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DOI：
10.1021/ja982933p
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发表时间：
1999-03-17
影响因子：
15
通讯作者：
Favaro, G
中科院分区：
文献类型：
--
作者：
Becker, RS;Pelliccioli, AP;Favaro, G
本文测量了光致变色分子（flindersine）的荧光量子产率（Phi（F））和反应量子产率（Phi（PC））与激发态电子振动能级（n）的关系。我们发现，Phi（F）减少和Phi（PC）增加的序列内激发的电子振动能级的量子数的增加。在先前提出的模型的基础上，这种行为被解释为导致振动弛豫和光化学之间的竞争，在每个电子振动水平。该模型被拓宽，并开发了一个新的方程，该方程单独或与荧光数据相结合，允许确定（1）部分产生的有色形式的摩尔消光系数，（2）振动弛豫的量子产率，Phi（V），和每个振动能级的互补Phi（PC），（3）光化学反应速率常数，kpc，（4）从S-1到S-0的无辐射内转换速率常数k（NR）。（5）S-1，k（V）的n个能级间的振动弛豫速率常数。k（PC）值（1.7 x 10（10）s（-1））与k（V）（4.0 x 10（10）s（-1））和k（NR）（2.3 x 10（10）s（-1））相当。数据和模型解释了Phi（F）随激发n值的增加而显著降低的现象。因此，从这里的结果以及从我们以前的工作，我们提出的理论，对于分子进行激发态光化学，将有他的振动能级的依赖性Phi（PC）和Phi（F）和潜在的三重态产量Phi（T）以及。它也似乎可以有一个振动模式和电子状态的依赖这些参数。光化学的性质也可能与模式有关。
In this paper we measured the fluorescence quantum yield (Phi(F)) and the reaction quantum yield (Phi(PC)) of a photochromic molecule (flindersine) as a function of the vibronic level (n) excited within a given sequence. We found that Phi(F) decreased and Phi(PC) increased with an increase in the quantum number of the vibronic level excited within a sequence. On the basis of a previously proposed model, this behavior was interpreted as resulting from competition between vibrational relaxation and photochemistry at each vibronic level. This model was broadened, and a new equation developed which, alone, or in combination with fluorescence data, permits determination of (1) the molar extinction coefficient of the partially produced colored form, (2) the quantum yield of vibrational relaxation, Phi(V), and the complementary Phi(PC) at each vibronic level, (3) the photochemical reaction rate constant, kpc, (4) the nonradiative internal-conversion rate constant from S-1 to S-0, k(NR). and (5) the vibrational relaxation rate constant among the n levels of S-1, k(V). The k(PC) value (1.7 x 10(10) s(-1)) is comparable to k(V) (4.0 x 10(10) s(-1)) and k(NR) (2.3 x 10(10)s(-1)). The data and model account fbr the significant decrease in Phi(F) with an increase in the value of n excited. Therefore, from the results here as well as those from our previous works, we propose the theory that for molecules undergoing excited-state photochemistry, there will he a vibronic-level dependence for Phi(PC) and Phi(F) and potentially for the triplet state yield Phi(T) as well. It also appears that there can be a vibronic-mode and electronic-state dependence for these parameters. The nature of the photochemistry could also well be mode-dependent.