Browsing by Author "Lin Sheng-Hsien"

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Anharmonic Effect of the Decomposition Reaction of Methyl Butanoate
(2016-11-15)
Ding Yang
;
Song Li-Guo
;
Yu Yi-Xuan
;
Yao Li
;
Lin Sheng-Hsien
In this paper, we have used the MP2/6-311++G(2d,2p) method to conduct a detailed investigation of the potential energy surface for the unimolecular dissociation reaction of methyl butanoate (MB). We have also used the Rice-Ramsperger-Kassel-Marcus (RRKM) theory to calculate the rate constants of the canonical and microcanonical systems at temperatures and total energies ranging from 1000 to 5000 K and 451.92 to 1519.52 kJ . mol(-1), respectively. The results indicated that there was an obvious anharmonic effect for the TS2, TS4 and TS5 pathways, and that this effect was too pronounced to be neglected for the unimolecular dissociation reactions of MB.
The anharmonic effect study of coupled Morse oscillators for the unimolecular reaction
(2008-12-01)
Yao Li
;
Lin Sheng-Hsien
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
The importance of anharmonic effect in dissociation of molecular systems especially clusters has been noted. In this paper, we shall study the effect of coupled anharmonic oscillator of the standard bilinear form (SBF) Morse oscillator (MO) potential on unimolecular reaction. We shall use the systematic theoretical approach, YL method, proposed by Yao and Lin (YAO L, et. al. J Phys Chem A, 2007, 111( 29): 6722-6729), which can evaluate anharmonic effects on the rate constants based on the transition state theory. In treating the anharmonic effect with the Morse oscillator potential on unimolecular reactions under collision-free conditions by using the RRKM (Rice-Ramsperger-Kassel-Marcus) theory, the inverse Laplace transformation of the partition functions was used to obtain the total amount of state and density of state by using the first-order and the second-order approximations of the saddle-point method. To demonstrate the anharmonic effect of the SBF Morse model, we choose some model systems and a real reaction as examples.
Theoretical study on S(1)((1)B(3u)) state electronic structure and absorption spectrum of pyrazine
(2008-12-01)
He RongXing
;
Zhu ChaoYuan
;
Chin Chih-Hao
;
Lin Sheng-Hsien
;
應用化學系分子科學碩博班
Making use of a set of quantum chemistry methods, the harmonic potential surfaces of the ground state (S(0)((1)A(g))) and the first (S(1)((1)B(3u))) 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 absorption spectrum of S(1)((1)B(3u)) state of pyrazine. The assignment of main vibronic transitions is made for S(1)((1)B(3u)) state. It is found that the spectral profile is mainly described by the Franck-Condon progression of totally symmetric mode v(6a). For the five totally symmetric modes, the present calculations show that the frequency differences between the ground and the S(1)((1)B(3u)) state are small. Therefore the displaced harmonic oscillator approximation along with Franck-Condon transition is used to simulate S(1)((1)B(3u)) 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 v(10a). The calculated S(1)((1)B(3u)) absorption spectrum is in reasonable agreement with the experimental spectra.
Theoretical study on S-1(B-1(3u)) state electronic structure and absorption spectrum of pyrazine
(2008-12-01)
He RongXing
;
Zhu ChaoYuan
;
Chin Chih-Hao
;
Lin Sheng-Hsien
;
應用化學系分子科學碩博班
Making use of a set of quantum chemistry methods, the harmonic potential surfaces of the ground state (S-0((1)A(g))) and the first (S-1(B-1(3u))) 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 absorption spectrum of S-1(B-1(3u)) state of pyrazine. The assignment of main vibronic transitions is made for S-1(B-1(3u)) state. It is found that the spectral profile is mainly described by the Franck-Condon progression of totally symmetric mode v(6a). For the five totally symmetric modes, the present calculations show that the frequency differences between the ground and the S-1(B-1(3u)) state are small. Therefore the displaced harmonic oscillator approximation along with Franck-Condon transition is used to simulate S-1(B-1(3u)) 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 v(10a). The calculated S-1(B-1(3u)) absorption spectrum is in reasonable agreement with the experimental spectra.