Photodissociation by Circularly Polarized Light Yields Photofragment Alignment in Ozone Arising Solely from Vibronic Interactions.
Photodissociation by Circularly Polarized Light Yields Photofragment Alignment in Ozone Arising Solely from Vibronic Interactions.
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DOI：
10.1103/physrevlett.122.083403
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发表时间：
2019-03
影响因子：
8.6
通讯作者：
Chaya Weeraratna;O. Vasyutinskii;A. Suits
中科院分区：
文献类型：
--
作者：
Chaya Weeraratna;O. Vasyutinskii;A. Suits
我们提出了一个直接测定的平面多原子分子光解的圆偏振光产生的光碎片的取向。这种对齐出现通过一个新的机制，涉及两个相互垂直的面内跃迁偶极矩分量的相干激发。通过一个新的各向异性参数γ_{2}^γ '}描述了这种取向，该参数由一个独特的激光偏振几何分离出来。在266 nm处获得O（^{1} D2}）原子碎片的直流切片图像，实现了臭氧光解过程中γ 2 ^β '}参数的测定。一个模型的光解机制的解释表明，它只能存在于失败的情况下的玻恩-奥本海默近似时，电子和振动（电子振动）的相互作用必须考虑。这一发现表明，确定取向参数γ_{2}^β '}可以作为直接了解多原子分子光解中电子振动相互作用的一个关键。通过Hartley带对臭氧光解的结果显示出明显的γ 2 ^π '}排列，但对反冲速度的依赖性很小，这与我们的实验条件下，与导数耦合的情况相反，非绝热动力学的振动贡献不依赖于反冲速度的观点一致。
We present a direct determination of photofragment alignment produced by circularly polarized light in photolysis of a planar polyatomic molecule. This alignment arises via a new mechanism involving coherent excitation of two mutually perpendicular in-plane transition dipole moment components. The alignment is described by a new anisotropy parameter γ_{2}^{'} that was isolated by a unique laser polarization geometry. The determination of the parameter γ_{2}^{'} was realized in ozone photolysis at 266 nm where dc slice images of O(^{1}D_{2}) atomic fragments were acquired. A model developed for interpretation of the photolysis mechanism shows that it can exist only in case of failure of the Born-Oppenheimer approximation when electronic and vibrational (vibronic) interactions have to be taken into account. This finding suggests that determination of the alignment parameter γ_{2}^{'} can be used as a key for direct insight into vibronic interactions in photolysis of polyatomic molecules. The results obtained for ozone photolysis via the Hartley band showed significant γ_{2}^{'} alignment but little recoil speed dependence, consistent with the notion that, as opposed to the situation for derivative coupling, under our experimental conditions, the vibronic contributions to the nonadiabatic dynamics are not dependent on recoil speed.