Title: Anharmonic Franck-Condon simulation of the absorption and fluorescence spectra for the low-lying S-1 and S-2 excited states of pyrimidine
Authors: Yang, Ling
Zhu, Chaoyuan
Yu, Jianguo
Lin, Sheng Hsien
Institute of Molecular science
Keywords: Harmonic and anharmonic simulation;Franck-Condon factors;Reorganization energy;Absorption and fluorescence spectra;Vibronic spectra
Issue Date: 25-May-2012
Abstract: Intensities and profiles of vibronic spectra of the low-lying singlet excited states were investigated with anharmonic and harmonic Franck-Condon simulations for pyrimidine. The first-order anharmonic correction shows dynamic shift of spectra that is exactly same as difference of reorganization energy between ground and excited states. The first-order correction show intensity enhancement of absorption and intensity weakening of fluorescence for S-1 state, and dynamic shift is also significant. On the other hand, the first-order correction is negligible for S-2 state. The main spectral progressions are well described by totally symmetry modes v(6a), v(1) and v(12). One mode from non-total symmetry v(16a) contributes to the weak band at 16a(2) transition for S-1 state. Four ab initio methods were employed in simulation; CASSCF, CASPT2, DFT and TD-DFT, and coupled-cluster singles-doubles (CCSD) and the equation-of-motion (EOM-CCSD) methods. They all work well, but CASSCF method show the best agreement with experiment for the weak-band intensities. (C) 2012 Elsevier B.V. All rights reserved.
URI: http://hdl.handle.net/11536/16299
ISSN: 0301-0104
Volume: 400
End Page: 126
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