The ultraviolet photodissociation of CS2: The S(1D2) channel
The ultraviolet photodissociation of CS2: The S(1D2) channel
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DOI：
10.1063/1.3678007
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发表时间：
2012-01-28
影响因子：
4.4
通讯作者：
Yuen, W. -H.
中科院分区：
文献类型：
--
作者：
Brouard, M.;Campbell, E. K.;Yuen, W. -H.
用速度图离子成像研究了CS2在193 nm和接近S（D-1（2））通道阈值的较长波长激发后的S（D-1（2））原子光碎片的光解。实验探测了能量势垒以上和以下的区域，以在（1）Sigma（+）（u）（B-1（2））势能面上线性。在两个区域的成像数据表明，S（D-1（2））原子产物的电子角动量是非极化的，但也揭示了不同的解离动力学在两个区域。在线性势垒之上的激发产生了反向的CS（（1）Sigma（+））振动布居分布，而在势垒之下激发后的长波长状态-状态结果显示了CS（（1）Sigma（+））（v，J）副产物状态分布，这与能量的统计分配一致。低于障碍，photorfragment激发光谱点的单重态通道的增强K = 1，相对于K = 0，其中K是沿沿着主轴的角动量的投影，与以前的工作。然而，CS共片段的产物态分布被发现是不敏感的K。有人提出，解离低于障碍线性主要发生在一个表面上具有显着的势能阱，没有出口通道障碍，如地面电子状态。然而，振荡结构中也观察到的动能释放分布，这被证明是一致的父分子弯曲运动的映射。这可能表明在线性屏障以下竞争性直接和间接解离机制的操作。(C)2012年美国物理学会。[doi 10.1063/1.3678007]
The photodissociation of CS2 has been investigated using velocity-map ion imaging of the S(D-1(2)) atomic photofragments following excitation at 193 nm and at longer wavelengths close to the S(D-1(2)) channel threshold. The experiments probe regions both above and below the energetic barrier to linearity on the (1)Sigma(+)(u)(B-1(2)) potential energy surface. The imaging data in both regions indicate that the electronic angular momentum of the S(D-1(2)) atom products is unpolarized, but also reveal different dissociation dynamics in the two regions. Excitation above the barrier to linearity yields an inverted CS((1)Sigma(+)) vibrational population distribution, whereas the long-wavelength state-to-state results following excitation below the barrier reveal CS((1)Sigma(+))(v, J) coproduct state distributions which are consistent with a statistical partitioning of the energy. Below the barrier, photofragment excitation spectra point to an enhancement of the singlet channel for K = 1, relative to K = 0, where K is the projection of the angular momentum along the principal axis, in agreement with previous work. However, the CS cofragment product state distributions are found to be insensitive to K. It is proposed that dissociation below the barrier to linearity occurs primarily on a surface with a significant potential energy well and without an exit channel barrier, such as that for the ground electronic state. However, oscillatory structure is also observed in the kinetic energy release distributions, which is shown to be consistent with a mapping of parent molecule bending motion. This could indicate the operation of competing direct and indirect dissociation mechanisms below the barrier to linearity. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3678007]