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Photodissociation Dynamics of Methanol and Ethanol at 157 nm
Kai-jun Yuan,Yuan Cheng,Feng-yan Wang,Xue-ming Yang*
Author NameAffiliationE-mail
Kai-jun Yuan State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China  
Yuan Cheng State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China  
Feng-yan Wang State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China  
Xue-ming Yang* State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China xmyang@dicp.ac.cn 
Abstract:
157 nm photodissociation of jet-cooled CH3OH and C2H5OH was studied using the high-n Rydberg atom time-of-flight (TOF) technique. TOF spectra of nascent H atom products were measured. Simulation of these spectra reveals three different atomic H loss processes: one from hydroxyl H elimination, one from methyl (ethyl) H elimination, and one from secondary dissociation of the methoxy (ethoxy) radical. The relative branching ratio indicates secondary dissociation of ethoxy is less important than that of methoxy. The average angular anisotropy parameter of methanol is negative (withβ≈-0.3), indicating the transition dipole moment is perpendicular to the C-O-H plane. The slightly more negative β value of ethanol (with β≈-0.4) implies that ethanol has a longer rotational period. These experimental results indicate that both systems undergo fast internal conversion to the 3s surface after it is excited to the 3px surface, and then dissociate on the 3s surface. The translational energy distribution of the CH3O+H products reveals extensive CH3 rocking or CH3 umbrella excitation in the CH3O radical. However the vibrational structures are not resolved in the C2H5O radical
Key words:  Photodissociation dynamics, H atom channel, VUV photolysis
FundProject:国家自然科学基金,国家重点基础研究规划项目
Photodissociation Dynamics of Methanol and Ethanol at 157 nm
袁开军,程元,王凤燕,杨学明*
摘要:
利用氢原子里德堡时间飞行谱技术研究了超音速喷射分子束CH3OH和C2H5OH在157 nm的光解动力学,得到了氢原子产物的时间飞行谱.通过对谱图的拟合揭示出三个氢原子产物通道:OH上的氢原子脱落、CH3(C2H5)上的氢原子脱落和CH3O(C2H5O)的二次解离. 从得到的产物通道相对分支比可以知道CH3O的二次解离过程比C2H5O更明显.CH3OH解离的产物平均角分布各向异性参数β≈-0.3, 显示出跃迁偶极距接近垂直于C-O-H平面.C2H5OH解离的产物β≈-0.4,表明C2H5OH有更长的转动周期. 实验结果显示两个系统都经历了从3px到3s势能面的快速内转换, 然后在3s势能面上解离.CH3O+H产物平动能分布显示出CH3O的伞形振动激发或者CH3的摇摆振动激发,而C2H5O+H产物平动能分布没有振动态分辨.
关键词:  光解动力学,氢原子通道,真空紫外光照射
DOI:10.1088/1674-0068/21/04/301-307
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