Theoretical study on S1(1B3u) state electronic structure and absorption spectrum of pyrazine

• 来源期刊: 中国科学B辑（英文版）
• 年，卷（期）: 2008,（12）
• 页码范围: 1166-1173
• 页数: 8页
• 语种: 英文
• DOI: 10.1007/s11426-008-0124-2

摘要

Making use of a set of quantum chemistry methods, the harmonic potential surfaces of the ground state (S0(1Ag)) and the first (S1(1B3u)) excited state of pyrazine are investigated, and the electronic structures of the two states are characterized. In the present study, the conventional quantum mechanical method, taking account of the Born-Oppenheimer adiabatic approximation, is adopted to simulate the absorp-tion spectrum of S1(1B3u) state of pyrazine. The assignment of main vibronic transitions is made for S1(1B3u) state. It is found that the spectral profile is mainly described by the Franck-Condon progression of totally symmetric mode v6a. For the five totally symmetric modes, the present calculations show that the frequency differences between the ground and the S1(1B3u) state are small. Therefore the displaced harmonic oscillator approximation along with Franck-Condon transition is used to simulate S1(1B3u)absorption spectra. The distortion effect due to the so-called quadratic coupling is demonstrated to be unimportant for the absorption spectrum, except the coupling mode v10a. The calculated S1(1B3u) ab-sorption spectrum is in reasonable agreement with the experimental spectra.