Anharmonic Franck-Condon simulation of the absorption and fluorescence spectra for the low-lying S-1 and S-2 excited states of pyrimidine

作者：Yang, Ling; Zhu, Chaoyuan^*; Yu, Jianguo; Lin, Sheng Hsien

来源：Chemical Physics, 2012, 400: 126-136.

DOI：10.1016/j.chemphys.2012.03.010

• Harmonic and anharmonic simulation
• Franck-Condon factors
• Reorganization energy
• Absorption and fluorescence spectra
• Vibronic spectra

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.

• 出版日期2012-5-25
• 单位北京师范大学; 哈尔滨工业大学