The dependence of the ultrafast relaxation kinetics of the S(2) and S(1) states in beta-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies.
The dependence of the ultrafast relaxation kinetics of the S(2) and S(1) states in beta-carotene homologs and lycopene on conjugation length studied by femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies.
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通过飞秒时间分辨吸收和克尔门荧光光谱研究了 β-胡萝卜素同系物和番茄红素中 S(2) 和 S(1) 态的超快弛豫动力学对共轭长度的依赖性。
DOI：
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发表时间：
2009
影响因子：
4.4
通讯作者：
M. Yoshizawa
中科院分区：
文献类型：
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作者：
D. Kosumi;M. Fujiwara;R. Fujii;R. Cogdell;H. Hashimoto;M. Yoshizawa
利用飞秒时间分辨吸收光谱和克尔门荧光光谱研究了具有不同共轭双键数n（n=7-15）和番茄红素（n=11）的全反式-β-胡萝卜素同系物的超快弛豫动力学。用时间分辨荧光法精确测定了S（2）（1（1）B（u）（+））光学允许态的非辐射弛豫速率。用时间分辨吸收测量方法研究了S（1）（2（1）A（g）（-））光禁态的动力学过程。应用能隙定律充分描述了S（1）弛豫速率对共轭长度的依赖关系。与此相反，S（2）的非辐射弛豫速率在n=9时有一个最小值，当n大于11时，表现出与能隙定律相反的关系。S（2）弛豫速率的这种反常行为可以通过在大的n值（例如n=11）处位于S（2）和S（1）状态之间的中间状态（这里称为S（x）状态）的存在来解释。这种中间状态的存在将导致以下顺序弛豫途径S（2）-->S（x）-->S（1）-->S（0）。基于这些激发单重态的势能曲线之间的圆锥形交叉点的模型可以很容易地解释衰变率和能隙之间的测量关系。
The ultrafast relaxation kinetics of all-trans-beta-carotene homologs with varying numbers of conjugated double bonds n(n=7-15) and lycopene (n=11) has been investigated using femtosecond time-resolved absorption and Kerr-gate fluorescence spectroscopies, both carried out under identical excitation conditions. The nonradiative relaxation rates of the optically allowed S(2)(1(1)B(u) (+)) state were precisely determined by the time-resolved fluorescence. The kinetics of the optically forbidden S(1)(2(1)A(g) (-)) state were observed by the time-resolved absorption measurements. The dependence of the S(1) relaxation rates upon the conjugation length is adequately described by application of the energy gap law. In contrast to this, the nonradiative relaxation rates of S(2) have a minimum at n=9 and show a reverse energy gap law dependence for values of n above 11. This anomalous behavior of the S(2) relaxation rates can be explained by the presence of an intermediate state (here called the S(x) state) located between the S(2) and S(1) states at large values of n (such as n=11). The presence of such an intermediate state would then result in the following sequential relaxation pathway S(2)-->S(x)-->S(1)-->S(0). A model based on conical intersections between the potential energy curves of these excited singlet states can readily explain the measured relationships between the decay rates and the energy gaps.
影响因子：
3.3
作者：
Niedzwiedzki, Dariusz;Koscielecki, Jeremy F.;Frank, Harry A.
通讯作者：
Frank, Harry A.
影响因子：
3.3
作者：
Niedzwiedzki, Dariusz M.;Sullivan, James O.;Frank, Harry A.
通讯作者：
Frank, Harry A.
影响因子：
3.3
作者：
Cong, Hong;Niedzwiedzki, Dariusz M.;Frank, Harry A.
通讯作者：
Frank, Harry A.