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Structural Dynamics of Phenyl Azide in Light-Absorbing Excited States:Resonance Raman and Quantum Mechanical Calculation Study
Rong-dan Yuan,Jia-dan Xue,Xu-ming Zheng
Author NameAffiliationE-mail
Rong-dan Yuan Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China  
Jia-dan Xue Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China  
Xu-ming Zheng Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018, China zxm@zstu.edu.cn 
Abstract:
The excited state structural dynamics of phenyl azide (PhN3) after excitation to the light absorbing S2(A'), S3(A'), and S6(A') states were studied using the resonance Raman spectroscopy and complete active space self-consistent field calculations. The vibrational spectra and the UV absorption bands were assigned on the basis of the Fourier transform (FT)-Raman, FT-infrared measurements, the density-functional theory computations and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 273.9, 252.7, 245.9, 228.7, 223.1, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PhN3. The results indicated that the structural dynamics in the S2(A'), S3(A'), and S6(A') states were significantly different. The crossing points of the potential energy surfaces, S2S1(1) and S2S1(2), were predicted to play a key role in the low-lying excited state decay dynamics, in accordance with Kasha's rule, and N7=N8 dissociation. Two decay channels initiated from the Franck-Condon region of the S2(A') state were predicted: the radiative S2,min→S0 radiative decay and the S2→S1 internal conversion through the crossing points S2S1(1)/S2S1(2).
Key words:  Phenyl azide  Structural dynamics  Decay dynamics  Resonance Raman spectroscopy  CASSCF calculation  Curve-crossing
FundProject:
苯基叠氮在光吸收激发态上的结构动力学-共振拉曼和量子力学计算研究
袁荣单,薛佳丹,郑旭明
摘要:
采用共振拉曼光谱学和完全活化空间自洽场方法研究了苯基叠氮被激发到S2(A')、S3(A')和S6(A')光吸收态后的结构动力学. 基于傅立叶变换拉曼、傅立叶变换红外、紫外、密度泛函计算和简正模式分析,指认了紫外吸收光谱和振动光谱. 获得了环己烷、乙腈和甲醇溶剂中273.9、252.7、245.9、228.7、223.1和208.8 nm等不同激发波长下的A、B和C带共振拉曼光谱,以探测Franck-Condon区域的结构动力学. CASSCF计算获得了单重电子激发态能量最低点和势能面交叉点的电子激发能和优化几何结构. 结果表明,苯基叠氮在S2(A')、S3(A')和S6(A')态上的激发态结构动力学各不相同. 与Kasha规则相符,S2S1(1)和S2S1(2)势能面交叉点在S2(A')激发态衰变动力学和N7=N8键解离中扮演着重要角色. 提出了两条主要衰减通道:S2,min→S0辐射通道和S2,FC(ππ*)→S2(ππ*)/S1(nπ*)→S1(nπ*)非辐射通道.
关键词:  苯基叠氮  结构动力学  衰减动力学  共振拉曼光谱  CASSCF计算  锥形交叉点
DOI:10.1063/1674-0068/29/cjcp1510213
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