A resonance Raman spectroscopic and CASSCF investigation of the Franck-Condon region structural dynamics and conical intersections of thiophene.
A resonance Raman spectroscopic and CASSCF investigation of the Franck-Condon region structural dynamics and conical intersections of thiophene.
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Franck-Condon 区域结构动力学和噻吩圆锥形交叉点的共振拉曼光谱和 CASSCF 研究。
DOI：
10.1063/1.3480361
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Weihai Fang
中科院分区：
文献类型：
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作者：
Xianjin Wu;Xuming Zheng;Huigang Wang;Yan;X. Guan;D. Phillips;Xuebo Chen;Weihai Fang
获得了噻吩在环己烷溶液中的共振拉曼光谱，激发波长为239.5和266 nm，与240 nm的第一强吸收带共振。 光谱表明，Franck-Condon区光解离动力学具有多维特征，主要沿着反应坐标运动，有6个完全对称模式和3个非完全对称模式.在754 cm（-1）处出现的C-S反对称伸缩+C-C=C弯曲模ν（21）（B（2））和在906 cm（-1）处出现的H（7）C（3）-C（4）H（8）扭曲模ν（9）（A（2））表明在Franck-Condon区存在两种不同类型的激发态之间的振动耦合或曲线交叉。 利用完全活性空间自洽场理论计算方法，确定了噻吩分子的电子跃迁能、激发态结构以及2（1）A（1）与1（1）B（2）或1（1）B（1）势能面之间的圆锥交点（1）B（1）/（1）A（1）和（1）B（2）/（1）A（1）.这些计算结果与噻吩的Franck-Condon区结构动力学相关。噻吩在最低单重激发态势能超曲面上的开环光解反应途径是通过C-S键断裂和通过锥形交点（1）B（1）/（1）A（1）进行的，而在最低单重激发态势能超曲面中，通过圆锥交点（1）B（2）/（1）A（1）的内转换通道是次要的衰变通道.
Resonance Raman spectra were acquired for thiophene in cyclohexane solution with 239.5 and 266 nm excitation wavelengths that were in resonance with ∼240 nm first intense absorption band. The spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mostly along the reaction coordinates of six totally symmetry modes and three nontotally symmetry modes. The appearance of the nontotally symmetry modes, the C-S antisymmetry stretch +C-C=C bend mode ν(21)(B(2)) at 754 cm(-1) and the H(7)C(3)-C(4)H(8) twist ν(9)(A(2)) at 906 cm(-1), suggests the existence of two different types of vibronic-couplings or curve-crossings among the excited states in the Franck-Condon region. The electronic transition energies, the excited state structures, and the conical intersection points (1)B(1)/(1)A(1) and (1)B(2)/(1)A(1) between 2 (1)A(1) and 1 (1)B(2) or 1 (1)B(1) potential energy surfaces of thiophene were determined by using complete active space self-consistent field theory computations. These computational results were correlated with the Franck-Condon region structural dynamics of thiophene. The ring opening photodissociation reaction pathway through cleavage of one of the C-S bonds and via the conical intersection point (1)B(1)/(1)A(1) was revealed to be the predominant ultrafast reaction channel for thiophene in the lowest singlet excited state potential energy hypersurface, while the internal conversion pathway via the conical intersection point (1)B(2)/(1)A(1) was found to be the minor decay channel in the lowest singlet excited state potential energy hypersurface.