標題: Anharmonic Franck-Condon Simulation of the Absorption and Fluorescence Spectra for the Low-Lying S(1) and S(2) Excited States of Pyridine
作者: Wang, Huan
Zhu, Chaoyuan
Yu, Jian-Guo
Lin, Sheng Hsien
應用化學系分子科學碩博班
Institute of Molecular science
公開日期: 31-十二月-2009
摘要: Anharmonic effects of the absorption and fluorescence spectra of pyridine molecule are studied and analyzed for the two-low lying singlet excited states S(1)((1)B(1)) and S(2)((1)B(2)). The complete active space self-consistent field (CASSCF) method is utilized to compute equilibrium geometries and all 27 vibrational normal-mode frequencies for the ground state and the two excited states. The present calculations show that the frequency differences between the ground and two excited states are small for the ten totally symmetric vibrational modes so that the displaced oscillator approximation can be used for spectrum Simulations. The Franck-Condon factors within harmonic approximation basically grasp the main features of molecular spectra, but simulated 0-0 transition energy position and spectrum band shapes are not satisfactorily good for S(1)((1)B(1)) absorption and fluorescence spectra in comparison with experiment observation. As the first-order anharmonic correction added to Franck-Condon factors, both spectrum positions and band shapes can be simultaneously improved for both absorption and fluorescence spectra. It is concluded that the present anharmonic correction produces a significant dynamic shifts for spectrum positions and improves spectrum band shapes as well. The detailed structures of absorption spectrum of S(2)((1)B(2)) state observed from experiment can be also reproduced with anharmonic Franck-Condon simulation, and these were not shown in the harmonic Franck-Condon simulation with either distorted or Duschinsky effects in the literature.
URI: http://dx.doi.org/10.1021/jp903585c
http://hdl.handle.net/11536/6302
ISSN: 1089-5639
DOI: 10.1021/jp903585c
期刊: JOURNAL OF PHYSICAL CHEMISTRY A
Volume: 113
Issue: 52
起始頁: 14407
結束頁: 14414
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