The excited-state dynamics of two functional Fe-carbene complexes, [Fe(bmip)₂]²⁺ (bmip = 2,6-bis(3-methyl-imidazole-1-ylidene)-pyridine) and [Fe(btbip)₂]²⁺ (btbip = 2,6-bis(3-tert-butyl-imidazole-1-ylidene)pyridine), are studied using the spin-vibronic model. In contrast to the usual projection of the ground state nuclear wave function onto an excited state surface, the dynamics are initiated by an explicit interaction term between the external time-dependent electric field (laser pulse) and the transition dipole moment of the molecule. The results show that the spin-vibronic model, as constructed directly from electronic structure calculations, exhibits erroneous, polarization-dependent relaxation dynamics stemming from artificial interference of coupled relaxation pathways. This is due to the lack of rotational invariance in the description of excitation into degenerate states. We introduce and discuss a correction using the spherical basis and complex transition dipole moments. This modification in the interaction Hamiltonian leads to rotationally invariant excitation and produces polarization-independent population dynamics.

中文翻译：

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在自旋振动量子动力学模拟中如何将核波包激发为电子简并态

两种功能性Fe-卡宾配合物[Fe（bmip）₂ ] ²⁺（bmip = 2,6-双（3-甲基-咪唑-1-亚胺基）-吡啶）和[Fe（btbip）的激发态动力学₂ ] ²⁺（btbip = 2,6-bis（3- tert-自旋振动模型研究了-丁基-咪唑-1-亚胺基吡啶）。与通常将基态核波函数投影到激发态表面上相反，动力学是由外部时变电场（激光脉冲）和分子的跃迁偶极矩之间的显式相互作用项引发的。结果表明，直接从电子结构计算中构建的自旋振动模型显示出源于耦合弛豫路径的人为干扰的错误的，极化相关的弛豫动力学。这是由于在描述为简并状态的激发时缺乏旋转不变性。我们介绍并讨论了使用球基和复变跃迁偶极矩进行的校正。