A 4D wave packet study of the CH3I photodissociation in the A-band. Comparison with femtosecond velocity map imaging experiments.
A 4D wave packet study of the CH3I photodissociation in the A-band. Comparison with femtosecond velocity map imaging experiments.
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A 波段 CH3I 光解离的 4D 波包研究。
DOI：
10.1063/1.3650718
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
L. Bañares
中科院分区：
文献类型：
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作者：
A. García;R. Nalda;J. Durá;J. González;L. Bañares
本文采用四自由度的波包模型，即C-I解离坐标、I-CH（3）弯曲模、CH（3）伞模和C-H对称伸缩模，对CH（3）I在A波段的时间分辨光解动力学进行了理论研究.获得了I碎片的自旋轨道基态和激发态以及CH（3）碎片的无振动和振动激发态（对称伸缩ν（1）和伞ν（2）模）的不同解离（非绝热）通道的时钟时间和最终产物态分布，并与飞秒速度图成像实验的结果进行了比较。波包计算能够很好地再现CH（3）（ν（1），ν（2））+I*（（2）P（1/2））解离通道（ν（1）= 0和ν（2）= 0，1，2）以及CH（3）（ν（1）= 0，ν（2）= 0）+I（（2）P（3/2））解离通道的实验反应时间。然而，该模型未能预测CH（3）（ν（1），ν（2））+I（（2）P（3/2））通道（ν（1），ν（2））=（0，1），（0，2）和（1，0））的实验时钟时间，即当CH（3）碎片沿着自旋轨道基态I原子被振动激发时。这些结果是类似的那些以前得到的三维波包模型，其有效性进行了讨论，在光的四维处理的结果。理论和实验之间发现的分歧的可能解释进行了讨论。
The time-resolved photodissociation dynamics of CH(3)I in the A-band has been studied theoretically using a wave packet model including four degrees of freedom, namely the C-I dissociation coordinate, the I-CH(3) bending mode, the CH(3) umbrella mode, and the C-H symmetric stretch mode. Clocking times and final product state distributions of the different dissociation (nonadiabatic) channels yielding spin-orbit ground and excited states of the I fragment and vibrationless and vibrationally excited (symmetric stretch ν(1) and umbrella ν(2) modes) CH(3) fragments have been obtained and compared with the results of femtosecond velocity map imaging experiments. The wave packet calculations are able to reproduce with very good agreement the experimental reaction times for the CH(3)(ν(1), ν(2))+I*((2)P(1/2)) dissociation channels with ν(1) = 0 and ν(2) = 0,1,2, and also for the channel CH(3)(ν(1) = 0, ν(2) = 0)+I((2)P(3/2)). However, the model fails to predict the experimental clocking times for the CH(3)(ν(1), ν(2))+I((2)P(3/2)) channels with (ν(1), ν(2)) = (0, 1), (0, 2), and (1, 0), that is, when the CH(3) fragment produced along with spin-orbit ground state I atoms is vibrationally excited. These results are similar to those previously obtained with a three-dimensional wave packet model, whose validity is discussed in the light of the results of the four-dimensional treatment. Possible explanations for the disagreements found between theory and experiment are also discussed.