Browsing by Author "Li, Ming-Chung"

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A theoretical study on the spectroscopy and the radiative and non-radiative relaxation rate constants of the S(0) (1)A(1)-S(1) (1)A(2) vibronic transitions of formaldehyde
(2010-01-01)
Lin, Chih-Kai
;
Li, Ming-Chung
;
Yamaki, Masahiro
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
We have carried out a close examination on the mathematical treatments and the first-principle computations concerning the vibronic transitions between the S(0) (1)A(1) and the S(1) (1)A(2) states of formaldehyde. The simulation of absorption spectrum was presented with peak intensities calculated according to vibronic-coupled transition dipole moments and Franck-Condon factors. The radiative and non-radiative transition rate constants from the excited to the ground states were calculated with formulas based on Fermi's golden rule. It is concluded that our simulated absorption spectrum between 300 and 360 nm, as well as the estimated relaxation rate constants, showed good agreements with experimental reports.
A theoretical study on the spectroscopy and the radiative and non-radiative relaxation rate constants of the S-0 (1)A(1)-S-1 (1)A(2) vibronic transitions of formaldehyde
(2010-01-01)
Lin, Chih-Kai
;
Li, Ming-Chung
;
Yamaki, Masahiro
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
We have carried out a close examination on the mathematical treatments and the first-principle computations concerning the vibronic transitions between the S-0 (1)A(1) and the S-1 (1)A(2) states of formaldehyde. The simulation of absorption spectrum was presented with peak intensities calculated according to vibronic-coupled transition dipole moments and Franck-Condon factors. The radiative and non-radiative transition rate constants from the excited to the ground states were calculated with formulas based on Fermi's golden rule. It is concluded that our simulated absorption spectrum between 300 and 360 nm, as well as the estimated relaxation rate constants, showed good agreements with experimental reports.
Quantum Chemistry Study on Internal Conversion of Diphenyldibenzofulvene in Solid Phase
(2011-12-22)
Li, Ming-Chung
;
Hayashi, Michitoshi
;
Lin, Sheng-Hsien
;
應用化學系
;
Department of Applied Chemistry
We investigate the nonradiative decay process of diphenyldibenzofulvene (DPDBF) in solid phase by using the quantum chemistry methods. To carry out the nonradiative rate constant calculation, we construct a solid phase model based on the ONIOM method. The geometry of the DPDBF molecule is optimized for the ground state by DFT and the first excited state by TD-DFT, and the corresponding vibrational frequencies and normal coordinates are computed. Under displaced-distorted harmonic oscillator potential approximation, Huang-Rhys factors are obtained. Vibronic coupling constants are calculated as a function of the normal mode based on Domcke's scheme. We find that vibronic coupling constants of 12 modes with large reorganization energies are of similar order, and if this result is still valid for other modes, the internal conversion rate would be determined by high frequency modes because they have a significant nuclear factor that is related to Franck-Condon overlap intergrals. We also find that geometrical changes are suppressed due to the stacking effect, which yields small Huang-Rhys values in the solid phase.