Intramolecular vibrational dynamics in S1 p-fluorotoluene. I. Direct observation of doorway states
Intramolecular vibrational dynamics in S1 p-fluorotoluene. I. Direct observation of doorway states
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DOI：
10.1063/1.3638689
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发表时间：
2011-09-28
影响因子：
4.4
通讯作者：
Reid, Katharine L.
中科院分区：
文献类型：
--
作者：
Davies, Julia A.;Reid, Katharine L.
利用皮秒时间分辨光电子能谱研究了S-118 a（1）在对氟甲苯（pFT）中激发后的分子内振动重分布（IVR），其中nu（18 a）是环弯曲振动模。在光电子信号中观察到周期为8 ps和5 ps的特征振荡，并归因于初始激发的零阶亮态和两个门口态之间的耦合。连接这三个振动状态的耦合系数的值已被确定。此外，光电子信号的指数变化与寿命为17 ps归因于较弱的耦合与浴的暗态，发挥更显着的作用，在IVR的后期阶段。使用层模型将最强耦合的门口态分配给S-117 a（1）6a '（2），其中nu（17 a）是CH面外振动模式，6a'（2）是甲基扭转能级。这一分配意味着扭转振动耦合机制介导所观察到的动力学，从而证明了甲基扭转模式在加速IVR中发挥的重要作用。(C)2011年美国物理学会。[doi：10.1063/1.3638689]
Picosecond time-resolved photoelectron spectroscopy is used to investigate intramolecular vibrational redistribution (IVR) following excitation of S-1 18a(1) in p-fluorotoluene (pFT) at an internal energy of 845 cm(-1), where nu(18a) is a ring bending vibrational mode. Characteristic oscillations with periods of 8 ps and 5 ps are observed in the photoelectron signal and attributed to coupling between the initially excited zero-order bright state and two doorway states. Values for the coupling coefficients connecting these three vibrational states have been determined. In addition, an exponential change in photoelectron signal with a lifetime of 17 ps is attributed to weaker couplings with a bath of dark states that play a more significant role during the latter stages of IVR. A tier model has been used to assign the most strongly coupled doorway state to S-1 17a(1) 6a'(2), where nu(17a) is a CH out-of-plane vibrational mode and 6a'(2) is a methyl torsional level. This assignment signifies that a torsion-vibration coupling mechanism mediates the observed dynamics, thus demonstrating the important role played by the methyl torsional mode in accelerating IVR. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638689]