The dynamical processes following photoexcitation of all-trans 2,4,6-octatriene to the two lowest singlet excited states are investigated theoretically, from two different points of view. The S₁-S₀ photoisomerization is characterized with a focus on structural aspects (stationary points and reactive modes), while for the UV-visible spectrum, arising from excitation to the S₂ state, nonadiabatic quantum dynamics calculations with four planar degrees of freedom are performed. The underlying electronic structure data are obtained from CASSCF and MS-CASPT2 ab initio computations, the quantum dynamical calculations rely on the Multiconfiguration Time-Dependent Hartree (MCTDH) method. The observed envelope of the UV-visible spectrum is well reproduced and the substantial broadness of the spectral features related to a nonradiative S₂-S₁ transition proceeding within few tens of femtoseconds. The vertical excitation energy from the A_g to the B_u state shows a red-shift (∼0.2 eV with the cc-pVTZ basis set) with reference to the all-trans hexatriene system. This affects the S₂-S₁ nonradiative decay, while the methylation of the terminal carbon atoms seems to have a minor influence on the photo-isomerization path.

从两种不同的观点，从理论上研究了全反式2,4,6-辛三烯光激发到两个最低单重态激发态后的动力学过程。该小号₁ -S ₀光致异构化，其特征在于，重点放在结构方面（驻点和反应模式），同时为紫外-可见光谱，从激发引起的小号₂状态下，非绝热量子动力学计算与四个平面自由度执行。基础电子结构数据从CASSCF和MS-CASPT2从头获得在计算中，量子动力学计算依赖于多配置时变哈特里（MCTDH）方法。观察到的紫外线-可见光谱的包络被很好地再现，并且与非辐射S ₂ -S ₁跃迁有关的光谱特征的相当宽的宽度在几十飞秒内进行。相对于全反己六烯系统，从A _g到B _u态的垂直激发能显示出红移（在cc-pVTZ基组下约为0.2 eV）。这会影响S ₂ -S ₁ 非辐射衰减，而末端碳原子的甲基化似乎对光异构化路径影响较小。