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

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• 作者：Yingli Niu ; Qian Peng ; Chunmei Deng ; Xing Gao ; Zhigang Shuai
• 刊名：Journal of Physical Chemistry A
• 出版年：2010
• 出版时间：August 5, 2010
• 年：2010
• 卷：114
• 期：30
• 页码：7817-7831
• 全文大小：628K
• 年卷期：v.114,no.30(August 5, 2010)
• ISSN：1520-5215

文摘

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., S₁ → S₀ and S₀ → S₁ of linear polyacenes, anthracene, tetracene, and pentacene, the HT effect is found to enhance the radiative decay rates by 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 S₁ → S₀ 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.