Picosecond IR-UV pump-probe spectroscopic study on the vibrational energy flow in isolated molecules and clusters.
Picosecond IR-UV pump-probe spectroscopic study on the vibrational energy flow in isolated molecules and clusters.
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DOI：
10.1039/b614895f
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发表时间：
2007-02
期刊：
影响因子：
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通讯作者：
Yuji Yamada;Yukiteru Katsumoto;T. Ebata
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文献类型：
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作者：
Yuji Yamada;Yukiteru Katsumoto;T. Ebata
用皮秒时间分辨IR-UV泵浦探测光谱研究了芳香族分子及其氢键簇合物的XH伸缩振动引起的分子内振动能重分布(IVR)和振动预解离(VP)。对于裸分子，我们主要关注苯酚的OH伸展的IVR。我们用两步层模型描述了OH伸缩的IVR，并用同位素替代法考察了非简谐耦合强度和态密度对IVR速率的影响和机制。在苯酚氢键簇合物中，我们证明了氢键伸缩振动的驰豫可以用一个逐步过程来描述，并讨论了哪个过程对氢键强度敏感。通过激发CH伸缩振动，讨论了苯酚-乙烯簇合物中“施主”和“受体”位置的IVR/VP的异同。最后，我们研究了具有烷基链的孤立分子，即苯乙醇(PA)中的振动能量转移。在这个体系中，我们测量了连接在烷基链两端的苯环振动和OH伸缩振动之间的振动能量转移的速率常数。这种能量传递可称为“直通债券IVR”。我们研究了被认为控制能量转移速率的三个因素：(1)“OH Next CH(2)”耦合，(2)链长和(3)构象。通过考察这些因素，我们讨论了PAS中的能量传递机制。
Intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) from the XH stretching vibrations, where X refers to O or C atom, of aromatic molecules and their hydrogen(H)-bonded clusters are investigated by picosecond time-resolved IR-UV pump probe spectroscopy in a supersonic beam. For bare molecules, we mainly focus on IVR of the OH stretch of phenol. We describe the IVR of the OH stretch by a two-step tier model and examine the effect of the anharmonic coupling strength and the density of states on IVR rate and mechanism by using isotope substitution. In the H-bonded clusters of phenol, we show that the relaxation of the OH stretching vibration can be described by a stepwise process and then discuss which process is sensitive to the H-bonding strength. We discuss the difference/similarity of IVR/VP between the "donor" and the "acceptor" sites in phenol-ethylene cluster by exciting the CH stretch vibrations. Finally, we study the vibrational energy transfer in the isolated molecules having the alkyl chain, namely phenylalcanol (PA). In this system, we measure the rate constant of the vibrational energy transfer between the OH stretch and the vibrations of benzene ring which are connected at the both ends of the alkyl chain. This energy transfer can be called "through-bond IVR". We investigate the three factors which are thought to control the energy transfer rate; (1) "OH next CH(2)" coupling, (2) chain length and (3) conformation. We discuss the energy transfer mechanism in PAs by examining these factors.