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Quenching of NCO(A2∑+) Radicals by Alkane Molecules
Hu Changjin, Huang Cunshui, Zhu Zhiqiang, Chen Yang*, Chen Congxiang*
Laboratory of Bond Selective Chemistry, Chinese Academy of Sciences, Department of Chemical Physics, University of Science and Technology of China, Hefei 230026
Abstract:
NCO radicals were produced by laser photolysis of CHBr3at 266 nm followed by the reaction of CH with N2O. The electronic ground state NCO radicals were electronically excited toA2Σ+(0000) state by laser irradiation at 438.6 nm. The quenching rate constants of NCO (A2Σ+) by CH4,n-C5H12,c-C6H12,n-C6H14, n-C7H16,n-C8H18were measured by investigating the time-resolved fluorescence from the excited NCO in room temperature (298 K). Removal was found to be very efficient where the rate constants with the above gases were measured as 2.35±0.14, 4.74±0.11, 4.65±0.12, 4.84±0.21, 5.15±0.19, 5.51±0.26, respectively, in units of 10~10 cm3/molec s. It is shown that the quenching rate constants and cross sections of NCO (A2Σ+) increase almost linearly with increasing the number of C-H bonds contained in the alkane molecules. By analysis, it is thought that chemical reactions play an important role in the quenching of the electronically excited NCO radicals and in addition to chemical reaction, collisional removal of NCO (A2Σ+) can take place via an E-V energy transfer.
Key words:  NCO radical, Alkane, Kinetics of quenching
FundProject:国家自然科学基金(29973038,10032050)、国家重点基础研究专项基金(G1999075304)资助项目.
烷烃类分子对NCO(A2∑+)自由基的猝灭
胡长进, 黄存顺, 朱志强, 陈旸*, 陈从香*
中国科学院选键化学重点实验室,中国科学技术大学化学物理系,合肥,230026
摘要:
采用激光光解-激光诱导荧光(LP-LIF)的方法,用266 nm激光光解CHBr3分子产生CH自由基,再与N2O继续反应作为NCO自由基的产生源,用438.6 nm激光将电子基态X2∏i(0010)的NCO激励到激发态A2∑+(00°0)上,通过检测激发态NCO时间分辨荧光信号,测得室温(298 K)下NCO(A2∑+)被烷烃类分子猝灭的实验结果,获得了A2∑+(00°0)态猝灭速率常数.实验发现,随着烷烃分子中C-H键数增加,其猝灭截面也近线性增加,但随着分子体积增大,这种增加趋缓.
关键词:  NCO自由基  烷烃分子  猝灭动力学
DOI:10.1088/1674-0068/16/2/84-88
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