Browsing by Author "Lin, Chih-Kai"

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A theoretical search for stable bent and linear structures of low-lying electronic states of the titanium dioxide (TiO(2)) molecule
(2011-01-01)
Lin, Chih-Kai
;
Li, Jun
;
Tu, Zheyan
;
Li, Xiangyuan
;
Hayashi, Michitoshi
In this work geometric optimization and potential energy surface (PES) scan for the TiO(2) molecule were carried out to find out possible stable structures by using quantum chemical calculations. The ground state (S(0) 1 (1)A(1)) has the only equilibrium with a symmetric bent structure, whereas the linear conformer is unstable. The first singlet excited state (S(1) 1 (1)B(2)), on the other hand, possesses two potential minima where one is bent around the Franck-Condon region and the other is linear. The second singlet excited state (S(2) 1 (1)A(2)) has only one minimum which is linear, and at which geometry the first two excited states degenerate. Other low-lying singlet and triplet excited states have been investigated accordingly. Among the functionals applied in the present DFT calculations, B3LYP gave results most close to available experimental data, while some recently developed ones including HSE06, omega B97X-D and CAM-B3LYP were not satisfactory for this small system. Ab initio methods such as CASSCF, CASPT2 as well as CCSD-related calculations have been applied, and the latter two showed good results similar to DFT/B3LYP.
A theoretical search for stable bent and linear structures of low-lying electronic states of the titanium dioxide (TiO2) molecule
(2011-01-01)
Lin, Chih-Kai
;
Li, Jun
;
Tu, Zheyan
;
Li, Xiangyuan
;
Hayashi, Michitoshi
In this work geometric optimization and potential energy surface (PES) scan for the TiO2 molecule were carried out to find out possible stable structures by using quantum chemical calculations. The ground state (S-0 1 (1)A(1)) has the only equilibrium with a symmetric bent structure, whereas the linear conformer is unstable. The first singlet excited state (S-1 1 B-1(2)), on the other hand, possesses two potential minima where one is bent around the Franck-Condon region and the other is linear. The second singlet excited state (S-2 1 (1)A(2)) has only one minimum which is linear, and at which geometry the first two excited states degenerate. Other low-lying singlet and triplet excited states have been investigated accordingly. Among the functionals applied in the present DFT calculations, B3LYP gave results most close to available experimental data, while some recently developed ones including HSE06, omega B97X-D and CAM-B3LYP were not satisfactory for this small system. Ab initio methods such as CASSCF, CASPT2 as well as CCSD-related calculations have been applied, and the latter two showed good results similar to DFT/B3LYP.
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.
Electronic sum-frequency generation (ESFG) spectroscopy: theoretical formulation of resonances with symmetry-allowed and symmetry-forbidden electronic excited states
(2017-01-01)
Lin, Chih-Kai
;
Lei, Jian
;
Lin, Yu-De
;
Lin, Sheng Hsien
;
應用化學系
Sum-frequency generation spectroscopy is a powerful tool for analysing molecular species and orientation configurations on a surface or an interface. In addition to conventional vibrational resonant techniques, the electronic resonant (electronic sum-frequency generation [ESFG]) ones have been developed recently. We have established the theoretical formulation of ESFG spectroscopy based on the susceptibility approach, considering resonances with both symmetry-allowed and symmetry-forbidden electronic excited states; derivatives of transition dipole moments and vibronic couplings beyond the Condon approximation were included. With the aid of density functional theory computations, simulated ESFG spectra in resonances with both types of excited states of acetone are demonstrated. [GRAPHICS] .
Electronic sum-frequency generation (ESFG) spectroscopy: Theoretical formulation of resonances with symmetry-allowed and symmetry-forbidden excited states
(2016-03-13)
Lin, Chih-Kai
;
Yeh, Yu-Lin
;
Lin, Sheng Hsien
;
應用化學系
;
Department of Applied Chemistry
Excitation properties of the H3 defect center in diamond: A theoretical study
(2009-06-16)
Lin, Chih-Kai
;
Chang, Huan-Cheng
;
Hayashi, M.
;
Lin, S. H.
;
應用化學系
Theoretical calculations on electronic excitation energies and absorption cross sections of the H3 defect center in diamond were performed. We constructed model clusters with up to 180 atoms to imitate the local environment of the defect center and conducted first-principle calculations. TD-DFT predicted most accurately vertical excitation energy, whereas TD-HF and CIS provided rough estimations for one- and two-photon absorption cross sections. It was found that a model cluster with a diameter larger than similar to 1.0 nm is required, while relatively low-cost level of theory and basis set are sufficient for characterizing the excitation properties. (c) 2009 Elsevier B.V. All rights reserved.
First-principles study on sum-frequency generation spectroscopy of methanol adsorbed on TiO2(110) surface: Effects of substrate and molecular coverages
(2019-05-14)
Shen, Zhitao
;
Lin, Chih-Kai
;
Zhu, Chaoyuan
;
Lin, Sheng Hsien
;
交大名義發表
In this work, starting from the general theory of sum-frequency generation (SFG), we proposed a computational strategy utilizing density functional theory with periodic boundary conditions to simulate the vibrational SFG of molecules/solid surface adsorption system. The method has been applied to the CH3OH/TiO2(110) system successfully. Compared with the isolated molecule model, our theoretical calculations showed that the TiO2 substrate can significantly alter the second-order susceptibilities of a methanol molecule which is directly related to the SFG intensity. In addition, the SFG spectra have obvious changes while the methanol coverage increases, especially for the OH vibration peaks. Our theoretical spectra agree reasonably well with experimental measurements at 1 ML coverage, and an interesting peak which is absent in the theoretical spectra is tentatively assigned to some CH3 stretch vibration of methanol adsorbed on the oxygen vacancy of TiO2.
Molecular Dynamics Insight into the Diverse Thermodynamic Behavior of a Beta-Hairpin Peptide
(2013-07-01)
Tsai, Min-Yeh
;
Yuan, Jian-Min
;
Yamaki, Masahiro
;
Lin, Chih-Kai
;
Lin, Sheng Hsien
The b-hairpin is a building block in the -sheet structure. Understanding the formation of the -hairpin may provide insight into the formation of -sheet structures in, for example, protein amyloids. In this study, we performed molecular dynamics (MD) simulations to investigate the temperature-dependent transition behaviors of the GB1 -hairpin peptide. The simulated results are analysed in terms of distances between pairs of peptide bonds and site-dependent dihedral angles. Our results show that the properties of the hairpin can be site-dependent and that the dependency is primarily associated with the hairpin's geometrical shape and specific interactions, such as hydrophobic clustering. Thus our study provides a foundation for the interpretation of probe-dependent experimental results.
One- and two-photon absorption properties of diamond nitrogen-vacancy defect centers: A theoretical study
(2008-09-28)
Lin, Chih-Kai
;
Wang, Yi-Hsieh
;
Chang, Huan-Cheng
;
Hayashi, M.
;
Lin, S. H.
The negatively charged nitrogen-vacancy defect center, (NV)(-), in diamond has been investigated theoretically for its one-and two-photon absorption properties involving the first excited state with the (3)A(2) -> (3)E transition. Time-dependent density functional theory (TD-DFT), configuration interaction with single excitation (CIS), and complete active space self-consistent field (CASSCF) were employed in this investigation along with the 6-31G(d) basis set. Diamond lattice models containing 24-104 carbon atoms were constructed to imitate the local environment of the defect center. TD-DFT calculations in large molecular cluster models (with 85 or more carbon atoms) predicted the vertical excitation energy quite consistent with the experimental absorption maximum. CASSCF calculations were feasible only for small cluster models (less than 50 carbon atoms) but yielded one-photon absorption (OPA) and two-photon absorption (TPA) cross sections somewhat larger than the experimental values obtained with linearly polarized incident light [T.-L. Wee et al., J. Phys. Chem. A 111, 9379 (2007)]. CIS calculations in larger cluster models showed a systematic overestimation of the excitation energy while just slightly underestimated the OPA cross section and overestimated the TPA cross section. The agreements between calculations and measurements suggest that the computational approaches established in this work are applicable to explore the optical properties of related defect centers in diamond as well. (C) 2008 American Institute of Physics.
Role of "dark" np* states in photoabsorption and relaxation processes of pyrazine
(2012-03-25)
Lin, Chih-Kai
;
Niu, Yingli
;
Lin, Sheng Hsien
;
應用化學系
;
Department of Applied Chemistry
Symmetry forbidden vibronic spectra and internal conversion in benzene
(2010)
Li, Jun
;
Lin, Chih-Kai
;
Li, Xiang Yuan
;
Zhu, Chao Yuan
;
Lin, Sheng Hsien
The spectra of symmetry-forbidden transitions and internal conversion were investigated in the present work. Temperature dependence was taken into account for the spectra simulation. The vibronic coupling, essential in the two processes, was calculated based on the Herzberg-Teller theory within the Born-Oppenheimer approximation. The approach was employed for the symmetry-forbidden absorption/fluorescence, and internal conversion between 1(1)A(1g) and 1(1)B(2u) states in benzene. Vibrational frequencies, normal coordinates, electronic transition dipole moments, and non-adiabatic coupling matrix elements were obtained by ab initio quantum chemical methods. The main peaks, along with the weak peaks, were in good agreement with the observed ones. The rate constant of the 1(1)A(1g) <- 1(1)B(2u) internal conversion was estimated within the order of 10(3) s(-1). This could be regarded as the lower limit (about 4.8 x 10(3) s(-1)) of the internal conversion. It is stressed that the distortion effect was taken into account both in the symmetry-forbidden absorption/fluorescence, and the rate constants of internal conversion in the present work. The distortion effects complicate the spectra and increase the rate constants of internal conversion.
The Role of the n pi* (1)A(u) State in the Photoabsorption and Relaxation of Pyrazine
(2011-11-04)
Lin, Chih-Kai
;
Niu, Yingli
;
Zhu, Chaoyuan
;
Shuai, Zhigang
;
Lin, Sheng Hsien
The geometric, energetic, and spectroscopic properties of the ground state and the lowest four singlet excited states of pyrazine have been studied by using DFT/TD-DFT, CASSCF, CASPT2, and related quantum chemical calculations. The second singlet n pi* state, (1)A(u), which is conventionally regarded dark due to the dipole-forbidden (1)A(u) <- (1)A(g) transition, has been investigated in detail. Our new simulation has shown that the state could be visible in the absorption spectrum by intensity borrowing from neighboring n pi* (1)B(3u) and pi pi* (1)B(2u) states through vibronic coupling. The scans on potential-energy surfaces further indicated that the (1)A(u) state intersects with the (1)B(2u) states near the equilibrium of the latter, thus implying its participation in the ultrafast relaxation process.
The visible spectrum of zirconium dioxide, ZrO(2)
(2011-09-14)
Le, Anh
;
Steimle, Timothy C.
;
Gupta, Varun
;
Rice, Corey A.
;
Maier, John P.
The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO(2), has been investigated using laser induced fluorescence (LW) in the region from 17 000 cm(-1) to 18 800 cm(-1) and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17 000 cm(-1)-21 000 cm(-1). The LIF and REMPI spectra are assigned to progressions in the (A) over tilde (1) B(2)(v(1), v(2), v(3)) <- (X) over tilde (1) A(1)(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the (X) over tilde (1) A(1) state of omega(1) = 898(1) cm(-1), omega(2) = 287(2) cm(-1), and omega(3) = 808(3) cm(-1). The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the (A) over tilde (1) B(2) state of T(e) = 16 307(8) cm(-1), omega(1) = 819(3) cm(-1), omega(2) = 149(3) cm(-1), and omega(3) = 518(4) cm(-1). The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the (A) over tilde (1) B(2) and (X) over tilde (1) A(1) states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO(2) is made. (C) 2011 American Institute of Physics. [doi:10.1063/1.3632053]
The visible spectrum of zirconium dioxide, ZrO2
(2011-09-14)
Le, Anh
;
Steimle, Timothy C.
;
Gupta, Varun
;
Rice, Corey A.
;
Maier, John P.
The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO2, has been investigated using laser induced fluorescence (LW) in the region from 17 000 cm(-1) to 18 800 cm(-1) and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17 000 cm(-1)-21 000 cm(-1). The LIF and REMPI spectra are assigned to progressions in the (A) over tilde (1) B-2(v(1), v(2), v(3)) <- (X) over tilde (1) A(1)(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the (X) over tilde (1) A(1) state of omega(1) = 898(1) cm(-1), omega(2) = 287(2) cm(-1), and omega(3) = 808(3) cm(-1). The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the (A) over tilde (1) B-2 state of T-e = 16 307(8) cm(-1), omega(1) = 819(3) cm(-1), omega(2) = 149(3) cm(-1), and omega(3) = 518(4) cm(-1). The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the (A) over tilde (1) B-2 and (X) over tilde (1) A(1) states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO2 is made. (C) 2011 American Institute of Physics. [doi:10.1063/1.3632053]
Theoretical formulation and computational simulation of electronic sum-frequency generation (ESFG) spectroscopy of surfactant on water surface
(2014-03-16)
Lin, Chih-Kai
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
;
應用化學系
;
Department of Applied Chemistry
Theoretical Formulation and Simulation of Electronic Sum-Frequency Generation Spectroscopy
(2013-11-14)
Lin, Chih-Kai
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
;
應用化學系
;
Department of Applied Chemistry
Sum-frequency generation (SFG) spectroscopy is a powerful tool for not only identifying molecular species but also analyzing orientation configurations on a surface/interface. In this Article, we presented reformulation of the theoretical framework of electronic SFG spectroscopy, the signal of which could be greatly enhanced by tuning one or two incident beam frequencies resonant with electronic excited states. Simulated electronic SFG spectra resonant at the sum frequency of a pair of coumarin-derivative pH-indicator surfactant molecules, 4-methyl-7-hydroxycoumarin and its anionic counterpart (MHC/MHC-), floating on the water surface were carried out as a demonstration.
Theoretical Study on Structure and Sum-Frequency Generation (SFG) Spectroscopy of Styrene-Graphene Adsorption System
(2013-01-31)
Lin, Chih-Kai
;
Shih, Chun-Chi
;
Niu, Yingli
;
Tsai, Min-Yeh
;
Shiu, Ying-Jen
In this theoretical study, we aimed to simulate the sum-frequency generation (SFG) spectroscopy of a thin polystyrene layer physically adsorbed on the graphene sheet and to figure out the orientation distribution of the phenyl units. To simplify the problem, we started the investigation by constructing molecular models with styrene and ethylbenzene monomers and styrene oligomers up to four units adsorbed on a finite-sized graphene hexagon. Geometric optimization results showed that the phenyl rings of the adsorbate always orientate close to the surface normal with a small tilt angle. The adsorption is weak but not negligible. SFG spectra have been simulated based on these calculated structures, vibrational frequencies, and dipole and polarizability derivatives to compare with experimental reports of polystyrene adsorbed on other surfaces.
Theoretical treatments of ultrafast electron transfer from adsorbed dye molecule to semiconductor nanocrystalline surface
(2006-10-21)
Liang, Kuo Kan
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Lin, Chih-Kai
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Chang, Huan-Cheng
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
In studying ultrafast electron transfer from a dye molecule to a nanosized semiconductor particle, pump-probe experiments are commonly used. In this system the electron transfer (ET) rate is faster than vibrational relaxation so that the ET rate should be described by a single-level rate constant and the probing signal (often in the form of time-resolved spectra) contains the contribution from the dynamics of both population and coherence (i.e., wave packet). In this paper, we shall present the theoretical treatments for femtosecond time-resolved pump-probe experiment and the dynamics of population and coherence by the density matrix method, and the calculation of single-level ET rate constant involved in a pump-probe experiment. As an application, we show the theoretical results using parameters extracted from experiments on a specific dye/semiconductor system. (c) 2006 American Institute of Physics.