Mode-specific excited-state dynamics of N-methylpyrrole.
Mode-specific excited-state dynamics of N-methylpyrrole.
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N-甲基吡咯的模式特定激发态动力学。
DOI：
10.1039/c9cp00113a
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Sang Kyu Kim
中科院分区：
文献类型：
--
作者：
Kyung Chul Woo;Sang Kyu Kim
用皮秒泵浦-探测方法测量了N-甲基吡咯S1态的态选择失活速率。S1衰变时间导致N-CH 3键解离被发现是强烈的模式依赖性表现在S1衰变和甲基片段生长动力学。时间分辨的速度图离子图像的stecCH 3片段，就高斯形的高动能分布的片段而言，表明N-CH 3裂解反应可能发生通过中间体。S1寿命在S1原点以上10700 cm-1处的突然减少伴随着玻尔兹曼型低动能分布的破碎。这个低动能碎片的出现速率非常慢，例如，与+806 cm-1带的S1寿命为174 ps相比，τ为5 ns，证实了先前的发现，即S1衰变过程开始被相应激发能区的新的快速非辐射跃迁所压倒。首先测量了由双光子吸收获得的S1原点处的寿命，得到τ = 8 ns。使用一个和两个光子吸收过程中，一些S1的电子振动带被确定为给模式依赖的寿命跨越一个非常宽的时间范围为8 ns-5 ps的相当窄的激发能区0-1800 cm-1以上的S1的起源。了解N-甲基吡咯动力学的多维激发态势能面上的能量耗散过程将得到很大的好处，从我们详细的模式特定的寿命测量。
State-selective deactivation rates of N-methylpyrrole in the S1 state have been measured by using the picosecond pump-probe method. The S1 decay time leading to the N-CH3 bond dissociation is found to be strongly mode-dependent as manifested in both S1 decay and methyl-fragment growth dynamics. Time-resolved velocity-map ion images of the ˙CH3 fragment, as far as the fragment of the Gaussian-shaped high kinetic energy distribution is concerned, suggest that the N-CH3 cleavage reaction might occur through an intermediate. Sudden decrease of the S1 lifetime at ∼700 cm-1 above the S1 origin is accompanied by the fragmentation of the Boltzmann-type low kinetic energy distribution. The appearance rate of this low-kinetic energy fragment turns out to be quite slow to give τ ∼ 5 ns compared to the S1 lifetime of ∼174 ps at the +806 cm-1 band, for instance, confirming previous findings that the S1 decay process starts to be overwhelmed by a new fast nonradiative transition in the corresponding excitation energy region. The lifetime at the S1 origin accessed by the two-photon absorption is firstly measured to give τ ∼ 8 ns. Using one and two photon absoption processes, a number of S1 vibronic bands are identified to give mode-dependent lifetimes spanning an enormously wide temporal range of 8 ns-5 ps in the quite narrow excitation energy region of 0-1800 cm-1 above the S1 origin. Understanding of the N-methylpyrrole dynamics on multidimensional excited-state potential energy surfaces governing energy dissipating processes will get much benefit from our detailed mode-specific lifetime measurements.
DOI：
10.1063/1.4938423
发表时间：
2016
期刊：
The Journal of chemical physics
影响因子：
--
作者：
Guorong Wu;S. Neville;O. Schalk;T. Sekikawa;M. Ashfold;G. Worth;A. Stolow
通讯作者：
Guorong Wu;S. Neville;O. Schalk;T. Sekikawa;M. Ashfold;G. Worth;A. Stolow