Ultrafast Laser-Induced Isomerization Dynamics in Acetonitrile
Ultrafast Laser-Induced Isomerization Dynamics in Acetonitrile
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DOI：
10.1021/acs.jpclett.0c01344
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发表时间：
2020-08-20
影响因子：
5.7
通讯作者：
Berrah, Nora
中科院分区：
文献类型：
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作者：
McDonnell, Matteo;LaForge, Aaron C.;Berrah, Nora
采用泵浦探测光谱结合离子-离子重合库仑爆炸成像技术研究了激光电离对乙腈（CH3CN）的异构化作用。我们推导出了5个主要通道，分别表示C-C直接分解、单氢和双氢迁移以及H和H-2在乙腈阳离子中的解离。令人惊讶的是，氢迁移通道比直接破碎更占优势。量子化学计算支持了这一观察结果，表明通过单氢和双氢迁移的异构化导致非常稳定的线性和环状异构体，其中大多数比母分子电离后的原始线性结构更稳定。这与以前使用类似方案研究的大多数分子不同。通过改变泵浦脉冲和探测脉冲之间的延迟，我们还确定了相应动力学过程的时间尺度。异构化通常发生在几百飞秒内，这个时间尺度与氢和氢-2解离和直接分子分裂的时间尺度相当。
Isomerization induced by laser ionization in acetonitrile (CH3CN) was investigated using pump-probe spectroscopy in combination with ion-ion coincident Coulomb explosion imaging. We deduced five primary channels indicating direct C-C breakup, single and double hydrogen migration, and H and H-2 dissociation in the acetonitrile cation. Surprisingly, the hydrogen-migration channels dominate over direct fragmentation. This observation is supported by quantum chemistry calculations showing that isomerization through single and double hydrogen migration leads to very stable linear and ring isomers, with most of them more stable than the original linear structure following ionization of the parent molecule. This is unlike most molecules investigated previously using similar schemes. By varying the delay between the pump and probe pulses, we have also determined the time scales of the corresponding dynamical processes. Isomerization typically occurs in a few hundred femtoseconds, a time scale that is comparable to that found for H and H-2 dissociation and direct molecular fragmentation.