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H-atom Dissociation Channels in Ultraviolet Photochemistry of m-PyridylRadical
Michael Lucas,Jasmine Minor,Jingsong Zhang*,Christopher Brazier
Author NameAffiliationE-mail
Michael Lucas Department of Chemistry, University of California, Riverside, CA 92521, USA  
Jasmine Minor Department of Chemistry, University of California, Riverside, CA 92521, USA  
Jingsong Zhang* Department of Chemistry, University of California, Riverside, CA 92521, USAAir Pollution Research Center, University of California, Riverside, CA 92521, USA jingsong.zhang@ucr.edu. 
Christopher Brazier Department of Chemistry and Biochemistry, California State University, Long Beach, CA 90840, USA  
Abstract:
The H atom production channels in the ultraviolet (UV) photochemistry of m-pyridyl radical (m-C5H4N) were investigated at excitation wavelengths from 224 nm to 248 nm by high-n Rydberg atom time-of-flight (HRTOF) technique. The photofragment yield (PFY) spectrum of the H atoms indicates a broad UV absorption feature near 234 nm. The product kinetic energy release is small; the average product kinetic energy at the wavelengths from 224 nm to 248 nm is 0.12 to 0.19 of the maximum excess energy (assuming the lowest energy product channel, H+cyanovinylacetylene). The product kinetic energy distributions are consistent with the H cyanovinylacetylene, H 3,4-pyridyne, and H 2,3-pyridyne product channels, with H cyanovinylacetylene as the main H-loss channel. The angular distributions of the H-atom products are isotropic. After the UV electronic excitation, the m-pyridyl radical undergoes internal conversion to the ground electronic state and then unimolecular dissoci-ation to the H cyanovinylacetylene, H 3,4-pyridyne, and H 2,3-pyridyne products. The dissociation mechanism of the m-pyridyl radical is similar to that of the o-pyridyl radical reported in the early study.
Key words:  Photolysis, Photofragment, Pyridyl, Pyridine, Decomposition, Excited state
FundProject:
间-吡啶基紫外光化学中的氢原子解离通道
Michael Lucas,Jasmine Minor,张劲松*,Christopher Brazier
摘要:
利用高里德堡态氢原子飞行时间探测技术, 在224~248 nm激发波长研究了间-吡啶基紫外光化学中的氢原子解离通道的动力学过程.氢原子光解碎片产率谱显示在234 nm附近有较宽的吸收.产物的平动能释放较小;在224~248 nm激发波长区间平均< fT>是0.12~0.19.产物的平动能分布显示产物是H+HC≡C-CH=CH-C≡N,H 3,4-吡啶和H 2,3-吡啶,以H HC≡C-CH=CH-C≡N为主要的氢原子生成通道.氢原子碎片具有各向同性的角度分布.研究结果表明,在紫外电子态激发以后,间-吡啶基经过内转换到电子基态,再经由单分子解离到H HC≡C-CH=CH-C≡N,H 3,4-吡啶和H 2,3-吡啶产物.间-吡啶基的紫外光解机理和以前报道过的邻-吡啶基的紫外光解机理相似.
关键词:  光解,光碎片,吡啶基,吡啶,解离,激发态
DOI:10.1063/1674-0068/27/06/621-627
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