Theory of Excited State Decays and Optical Spectra: Application to Polyatomic Molecules

Abstract

General formalism of absorption and emission spectra, and of radiative and nonradiative decay rates are derived using a thermal vibration correlation function formalism for the transition between two adiabatic electronic states in polyatomic molecules. Displacements, distortions, and Duschinsky rotation of potential energy surfaces are included within the framework of a multidimensional harmonic oscillator model. The Herzberg-Teller (HT) effect is also taken into account. This formalism gives a reliable description of the Q(x) spectral band of free-base porphyrin with weakly electric dipole-allowed transitions. For the strongly dipole-allowed transitions, e.g., S(1) --> S(0) and S(0) --> S(1) of linear polyacenes, anthracene, tetracene, and pentacene, the HT effect is found to enhance the radiative decay rates by approximately 10% compared to those without the HT effect. For nonradiative transition processes, a general formalism is presented to extend the application scope of the internal conversion theory by going beyond the promoting-mode approximation. Numerical calculations for the nonradiative S(1) --> S(0) decay rate of azulene well explain the origin of the violation of Kasha's rule. When coupled with first-principles density functional theory (DFT) calculations, the present approach appears to be an effective tool to obtain a quantitative description and detailed understanding of spectra and photophysical processes in polyatomic molecules.

Theoretical and experimental determination of the absorption and emission spectra of a prototypical indolenine-based squaraine dye

“…This approach has been recently applied to the simulation of spectral lineshapes of large molecules 58 as well as to the determination of electron-transfer rates with positive results. 18,19,53 …”

“…1,2 Fast growing research fields such as organic LED technology 3 and dye-sensitized solar cells (DSSC), 4 would strongly benefit from the application of robust and easy-to-use methodologies for the simulation of spectral lineshapes of organic dyes. The research in this field is quickly growing [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] (see also Borrelli et al 22 for a recent review) but standardize procedures have not yet been established, and specific computational strategies must be carefully designed and require validation and testing on several class of molecules. [23][24][25][26] In this paper we apply state of the art tools of computational spectroscopy to simulate the absorption and emission lineshapes of squaraine dyes in solution.…”

Vibration Correlation Function Investigation on the Phosphorescence Quantum Efficiency and Spectrum for Blue Phosphorescent Ir(III) Complex

“…通过将正则模式变换到笛卡尔坐标, 耦合元能转换 成在对所有原子核处点电荷的电场求和, 从而可以在量 子化学水平上计算 [18] . 根据两电子态的电子结构信息, 根据 Eckart 转动条 件确定两电子态平衡位形关系, 采用笛卡尔坐标系计算 出体系的 Duschinsky 转动矩阵和位移矢量 [18] .…”

“…根据两电子态的电子结构信息, 根据 Eckart 转动条 件确定两电子态平衡位形关系, 采用笛卡尔坐标系计算 出体系的 Duschinsky 转动矩阵和位移矢量 [18] . 最后, 结 合分子的跃迁性质, 使用本组自主发展的光谱和速率理 论程序, 计算出有机过渡金属配合物 fac-Ir(F 2 ppy) 3 在不 同温度下的磷光光谱、辐射衰减速率和系间窜越速率、 磷光效率及激发态寿命.…”

Quantum Dynamics of Radiationless Electronic Transitions Including Normal Modes Displacements and Duschinsky Rotations: A Second-Order Cumulant Approach

“…modes whose quantum state can change upon transition, and solving numerically the associated time-dependent Schrödinger equation; ii) to resort to time-dependent perturbation theory for approximate solutions of the Schrödinger equation, retaining the whole space of coordinates or momenta. [7][8][9][10][11][12] Obviously, the choice between the two alternative approaches should be based on a careful analysis of the potential energies of the two electronic states involved in the transition.…”