The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform
Yong Zhang - One of the best experts on this subject based on the ideXlab platform.
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probing highly efficient photoisomerization of a bridged azobenzene by a combination of caspt2 CASSCF Calculation with semiclassical dynamics simulation
Journal of Physical Chemistry A, 2011Co-Authors: Shuai Yuan, Wei-hai Fang, Yong ZhangAbstract:Mechanism of phototriggered isomerization of azobenzene and its derivatives is of broad interest. In this paper, the S0 and S1 potential energy surfaces of the ethylene-bridged azobenzene (1) that was recently reported to have highly efficient photoisomerization were determined by ab initio electronic structure Calculations at different levels and further investigated by a semiclassical dynamics simulation. Unlike azobenzene, the cis isomer of 1 was found to be more stable than the trans isomer, consistent with the experimental observation. The thermal isomerization between cis and trans isomers proceeds via an inversion mechanism with a high barrier. Interestingly, only one minimum-energy conical intersection was determined between the S0 and S1 states (CI) for both cis → trans and trans → cis photoisomerization processes and confirmed to act as the S1 → S0 decay funnel. The S1 state lifetime is ∼30 fs for the trans isomer, while that for the cis isomer is much longer, due to a redistribution of the init...
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Probing Highly Efficient Photoisomerization of a Bridged Azobenzene by a Combination of CASPT2//CASSCF Calculation with Semiclassical Dynamics Simulation
Journal of Physical Chemistry A, 2011Co-Authors: Shuai Yuan, Wei-hai Fang, Yong ZhangAbstract:Mechanism of phototriggered isomerization of azobenzene and its derivatives is of broad interest. In this paper, the S0 and S1 potential energy surfaces of the ethylene-bridged azobenzene (1) that was recently reported to have highly efficient photoisomerization were determined by ab initio electronic structure Calculations at different levels and further investigated by a semiclassical dynamics simulation. Unlike azobenzene, the cis isomer of 1 was found to be more stable than the trans isomer, consistent with the experimental observation. The thermal isomerization between cis and trans isomers proceeds via an inversion mechanism with a high barrier. Interestingly, only one minimum-energy conical intersection was determined between the S0 and S1 states (CI) for both cis → trans and trans → cis photoisomerization processes and confirmed to act as the S1 → S0 decay funnel. The S1 state lifetime is ∼30 fs for the trans isomer, while that for the cis isomer is much longer, due to a redistribution of the init...
Wei-hai Fang - One of the best experts on this subject based on the ideXlab platform.
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The combined CASPT2 and CASSCF studies on photolysis of 3-thienyldiazomethane and subsequent reactions
Theoretical Chemistry Accounts, 2014Co-Authors: Pei-jie Guan, Wei-hai FangAbstract:The triplet 3- thienylcarbene and α - thial - methylenecyclopropene were observed as the main products upon photolysis ( λ > 540 nm) of 3- thienyldiazomethane (3-TD) under the matrix-isolated conditions. The underlying mechanism was explored by the combined CASPT 2 and CASSCF Calculation in the present work. The S1 , T2 , and T1 surfaces were found to be quasi-degenerate over a wide structural region. Meanwhile, there is a relatively strong spin – orbit interaction between the S 1 and T 2 states, due to the sulfur-atom effect. As a result, the triplet 3- thienylcarbene can be formed with a noticeable effi - ciency. The S1 minimum and S1 /S0 intersection structures for 3-TD were predicted to be undistinguishable by the present CASPT 2// CASSCF Calculations. Therefore, the S1 → S0 internal conversion that occurs in the vicinity of the S1 /S0 intersection (S1 minimum) is in competition with the S1 → T1 intersystem crossing through the three-surface (S1 , T2 , and T1 ) intersection region. Once the excited 3-TD molecule returns to the S 0 state, the singlet 3- thienylcarbene can be generated with a considerable effi ciency, which is followed by the carbene rearrangement, leading to the fi nal product of α - thial-methylenecyclopropene ( α - TMC ). The concerted N2 loss and rearrangement in the excited state was proposed for the α - TMC formation in previous experimental study, which is not supported by the present CASPT 2// CASSCF Calculation. The reason for this might come from the matrix effect, which is open for further study.
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vibronic coupling and excited state reaction dynamics of pyrazine in 1 1b2u 1ππ state by resonance raman spectroscopy and CASSCF Calculation
Journal of Raman Spectroscopy, 2012Co-Authors: Yanying Zhao, Wei-hai Fang, Huigang Wang, Xuming Zheng, Yuejie Ai, Xuebo Chen, Chi Shun YeungAbstract:The photophysics and photochemistry of pyrazine (C4H4N2, D2h) after excitation to the S2 (1 1B2u, 1ππ*) electronic state were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method Calculations. The B-band resonance Raman spectra in cyclohexane solvent were obtained at 266.0, 252.7, and 245.9 nm excitation wavelengths to probe the structural dynamics of pyrazine in the S2 (1 1B2u, 1ππ*) state. Three electronic states 1 1B3u, 1 1B1g, and 1 1B2g were found to couple with the S2 (1 1B2u, 1ππ*) state. Two conical intersection (CI) points CI[S2(B2u)/S1(B3u)] and CI[S1/S0] and one transition state of the isomerization between pyrazine and pyrimidine were predicted to play important roles in the photochemistry of pyrazine. On the basis of the Calculations, the mechanism of the photoisomerization reaction between pyrazine and pyrimidine has been proposed. Copyright © 2012 John Wiley & Sons, Ltd.
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probing highly efficient photoisomerization of a bridged azobenzene by a combination of caspt2 CASSCF Calculation with semiclassical dynamics simulation
Journal of Physical Chemistry A, 2011Co-Authors: Shuai Yuan, Wei-hai Fang, Yong ZhangAbstract:Mechanism of phototriggered isomerization of azobenzene and its derivatives is of broad interest. In this paper, the S0 and S1 potential energy surfaces of the ethylene-bridged azobenzene (1) that was recently reported to have highly efficient photoisomerization were determined by ab initio electronic structure Calculations at different levels and further investigated by a semiclassical dynamics simulation. Unlike azobenzene, the cis isomer of 1 was found to be more stable than the trans isomer, consistent with the experimental observation. The thermal isomerization between cis and trans isomers proceeds via an inversion mechanism with a high barrier. Interestingly, only one minimum-energy conical intersection was determined between the S0 and S1 states (CI) for both cis → trans and trans → cis photoisomerization processes and confirmed to act as the S1 → S0 decay funnel. The S1 state lifetime is ∼30 fs for the trans isomer, while that for the cis isomer is much longer, due to a redistribution of the init...
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Probing Highly Efficient Photoisomerization of a Bridged Azobenzene by a Combination of CASPT2//CASSCF Calculation with Semiclassical Dynamics Simulation
Journal of Physical Chemistry A, 2011Co-Authors: Shuai Yuan, Wei-hai Fang, Yong ZhangAbstract:Mechanism of phototriggered isomerization of azobenzene and its derivatives is of broad interest. In this paper, the S0 and S1 potential energy surfaces of the ethylene-bridged azobenzene (1) that was recently reported to have highly efficient photoisomerization were determined by ab initio electronic structure Calculations at different levels and further investigated by a semiclassical dynamics simulation. Unlike azobenzene, the cis isomer of 1 was found to be more stable than the trans isomer, consistent with the experimental observation. The thermal isomerization between cis and trans isomers proceeds via an inversion mechanism with a high barrier. Interestingly, only one minimum-energy conical intersection was determined between the S0 and S1 states (CI) for both cis → trans and trans → cis photoisomerization processes and confirmed to act as the S1 → S0 decay funnel. The S1 state lifetime is ∼30 fs for the trans isomer, while that for the cis isomer is much longer, due to a redistribution of the init...
Shuai Yuan - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of laser induced reactions of stacked benzene molecules a semiclassical dynamics simulation and CASSCF Calculation
International Journal of Photoenergy, 2014Co-Authors: Jie Zhao, Shuai Yuan, Glenn V LoAbstract:The response to ultrashort laser pulses of two stacked benzene molecules has been studied by semiclassical dynamics simulation; two typical pathways were found following excitation of one of the benzene molecules by a 25 fs (FWHM), 4.7 eV photon. With a fluence of 40.49 J/m2, the stacked molecules form a cyclobutane benzene dimer; the formation of the two covalent bonds linking two benzenes occurs asynchronously after the excimer decays to electronic ground state. With a fluence of 43.26 J/m2, only one bond is formed, which breaks about 50 fs after formation, followed by separation into the two molecules. The deformation of benzene ring is found to play an important role in the bond cleavage.
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probing highly efficient photoisomerization of a bridged azobenzene by a combination of caspt2 CASSCF Calculation with semiclassical dynamics simulation
Journal of Physical Chemistry A, 2011Co-Authors: Shuai Yuan, Wei-hai Fang, Yong ZhangAbstract:Mechanism of phototriggered isomerization of azobenzene and its derivatives is of broad interest. In this paper, the S0 and S1 potential energy surfaces of the ethylene-bridged azobenzene (1) that was recently reported to have highly efficient photoisomerization were determined by ab initio electronic structure Calculations at different levels and further investigated by a semiclassical dynamics simulation. Unlike azobenzene, the cis isomer of 1 was found to be more stable than the trans isomer, consistent with the experimental observation. The thermal isomerization between cis and trans isomers proceeds via an inversion mechanism with a high barrier. Interestingly, only one minimum-energy conical intersection was determined between the S0 and S1 states (CI) for both cis → trans and trans → cis photoisomerization processes and confirmed to act as the S1 → S0 decay funnel. The S1 state lifetime is ∼30 fs for the trans isomer, while that for the cis isomer is much longer, due to a redistribution of the init...
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Probing Highly Efficient Photoisomerization of a Bridged Azobenzene by a Combination of CASPT2//CASSCF Calculation with Semiclassical Dynamics Simulation
Journal of Physical Chemistry A, 2011Co-Authors: Shuai Yuan, Wei-hai Fang, Yong ZhangAbstract:Mechanism of phototriggered isomerization of azobenzene and its derivatives is of broad interest. In this paper, the S0 and S1 potential energy surfaces of the ethylene-bridged azobenzene (1) that was recently reported to have highly efficient photoisomerization were determined by ab initio electronic structure Calculations at different levels and further investigated by a semiclassical dynamics simulation. Unlike azobenzene, the cis isomer of 1 was found to be more stable than the trans isomer, consistent with the experimental observation. The thermal isomerization between cis and trans isomers proceeds via an inversion mechanism with a high barrier. Interestingly, only one minimum-energy conical intersection was determined between the S0 and S1 states (CI) for both cis → trans and trans → cis photoisomerization processes and confirmed to act as the S1 → S0 decay funnel. The S1 state lifetime is ∼30 fs for the trans isomer, while that for the cis isomer is much longer, due to a redistribution of the init...
Bo Zhou - One of the best experts on this subject based on the ideXlab platform.
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landscapes of four enantiomer conical intersections for photoisomerization of stilbene CASSCF Calculation
Journal of Physical Chemistry A, 2014Co-Authors: Le Yu, Bo ZhouAbstract:The photoisomerization of cis- and trans-stilbene through conical intersections (CI) is mainly governed by four dihedral angles around central C═C double bonds. The two of them are C—C═C—C and H—C═C—H dihedral angles that are found to form a mirror rotation coordinate, and the mirror plane appears at the two dihedral angles equal to zeros with which the middle state is defined through partial optimization. There exist the first-type of hula-twist-CI enantiomers, the second-type of hula-twist-CI enantiomers, the first-type of one-bond-flip-CI enantiomers, and the second type of one-bond-flip-CI enantiomers as well as cis-enantiomers and trans-enantiomers with respect to this mirror plane. The complete active space self-consistent field method is employed to calculate minimum potential energy profile along the mirror rotation coordinate for each enantiomers, and it is found that the left-hand manifold and the right-hand manifold of potential energy surfaces can be energetically transferred via photoisomeriz...
Chi Shun Yeung - One of the best experts on this subject based on the ideXlab platform.
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vibronic coupling and excited state reaction dynamics of pyrazine in 1 1b2u 1ππ state by resonance raman spectroscopy and CASSCF Calculation
Journal of Raman Spectroscopy, 2012Co-Authors: Yanying Zhao, Wei-hai Fang, Huigang Wang, Xuming Zheng, Yuejie Ai, Xuebo Chen, Chi Shun YeungAbstract:The photophysics and photochemistry of pyrazine (C4H4N2, D2h) after excitation to the S2 (1 1B2u, 1ππ*) electronic state were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method Calculations. The B-band resonance Raman spectra in cyclohexane solvent were obtained at 266.0, 252.7, and 245.9 nm excitation wavelengths to probe the structural dynamics of pyrazine in the S2 (1 1B2u, 1ππ*) state. Three electronic states 1 1B3u, 1 1B1g, and 1 1B2g were found to couple with the S2 (1 1B2u, 1ππ*) state. Two conical intersection (CI) points CI[S2(B2u)/S1(B3u)] and CI[S1/S0] and one transition state of the isomerization between pyrazine and pyrimidine were predicted to play important roles in the photochemistry of pyrazine. On the basis of the Calculations, the mechanism of the photoisomerization reaction between pyrazine and pyrimidine has been proposed. Copyright © 2012 John Wiley & Sons, Ltd.