Tunneling Dynamics of the NH3 (脙) State Observed by Time-Resolved Photoelectron and H Atom Kinetic Energy Spectroscopies

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• 作者：Hui Yu ; Nicholas L. Evans ; Adam S. Chatterley ; Gareth M. Roberts ; Vasilios G. Stavros ; Susanne Ullrich
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：October 9, 2014
• 年：2014
• 卷：118
• 期：40
• 页码：9438-9444
• 全文大小：381K
• ISSN：1520-5215

文摘

We have investigated the effects of quantum tunneling on the photodissociation dynamics of ammonia, following below and above barrier photoexcitation of low-lying levels of the 谓₂^{鈥?/sup> umbrella mode of the NH₃ 脙 state (NH₃ (脙)). This barrier separates the local minimum of the vertical Franck鈥揅ondon region from the NH₃ (脙)/NH₃ (X虄) conical intersection (CI) which can be accessed along the N鈥揌 stretch coordinate. Two complementary techniques, time-resolved photoelectron spectroscopy (TR-PES) and time-resolved total kinetic energy release spectroscopy (TR-TKER), have been utilized to directly measure, for the first time, vibrational level dependent excited state lifetimes and N鈥揌 dissociation time scales as well as photoproduct final energy distributions. Interestingly, 谓₂鈥?/sup> even/odd dependencies are observed in the measured time constants and NH₂ internal energy spectra, which are attributed to tunneling through a barrier, whose magnitude is dependent on the planarity of NH₃ in the 脙 state and direct versus indirect dissociation at the NH₃ (脙)/NH₃ (X虄) conical intersection.}