The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through F... more The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through FC simulation interpretation.
A large amount of complicated reaction networks of intermediates and radicals taken place in the ... more A large amount of complicated reaction networks of intermediates and radicals taken place in the pyrolysis of 2,5-dimethylfuran have been investigated based on the density function theory (DFT) and the sophisticated wave function theory (WFT) methodologies. The preliminary focus is concentrated on those without the furan-ring opening reaction processes. Calculations are performed for electronic structures, stability and electronic spectra of ground states and excited states for those intermediates and radicals. It is found that both low-lying valence excited states and Rydberg states (3s, 3px, 3py and 3pz) of the pyrolytic species might be involved in pyrolysis and combustion of 2,5-dimethylfuran and influence their chemical reaction kinetics. A generous tendency is also found that the vertical transition energies of the similar transitions become bigger with the removal of methyl in the furan ring.
ABSTRACT Recent rapid progress in quantum chemical calculations has made it possible to perform t... more ABSTRACT Recent rapid progress in quantum chemical calculations has made it possible to perform the first principle calculations of various molecular spectroscopies and photophysical processes. Anharmonic effect on molecular electronic absorption and luminescence like fluorescence and phosphorescence spectroscopies and electronic relaxation processes like internal conversion and intersystem crossing has been theoretically developed 10 years ago. This chapter reviews its applications to pyridine, pyrimdine, pyrazine, and fluorobenzene. It then presents the molecular theories of all types of sum-frequency generation (SFG) including both vibrational SFG (VSFG) and electronic SFG (ESFG). A couple of SFG examples based on the quantum chemical calculations are included for demonstration. The chapter presents how to perform the calculations of the intramolecular vibrational redistribution (IVR) for water clusters and amino acid molecules and their peptides. It applies the femto-second (fs) time-resolved density matrix method to treat the Bixon–Jortner (B-J) model which is a popular method for studying photophysical process.
Recently, the Landau-Zener-Stueckelberg problems have been completely solved in a form convenient... more Recently, the Landau-Zener-Stueckelberg problems have been completely solved in a form convenient for various applications. A summary of the results will be reported. Other related subjects such as multi-level curve crossing and conical intersection problems will also be briefly touched upon.
The density matrix method is a powerful theoretical technique to describe the ultrafast processes... more The density matrix method is a powerful theoretical technique to describe the ultrafast processes and to analyze the femtosecond time-resolved spectra in the pump-probe experiment. The dynamics of population and coherence of the system can be described by the evolution of density matrix elements. In this chapter, the applications of density matrix method on internal conversion and vibrational relaxation processes will be presented. As an example, the ultrafast internal conversion process of ππ* → nπ* transition of pyrazine will be presented, in which case the conical intersection is commonly believed to play an important role. A treatment with Q-dependent nonadiabatic coupling will be applied to deal with the internal conversion rate. Another important ultrafast process, vibrational relaxation, which usually takes place in sub-ps and ps range, will be treated using adiabatic approximation. Then the vibrational relaxation in water dimer and aniline will be chosen to demonstrate the c...
The emission spectra of triphenylamine salicylaldehyde derivatives are weak in solution and stron... more The emission spectra of triphenylamine salicylaldehyde derivatives are weak in solution and strong in the crystal, as interpreted by molecular spectral and dynamics simulations.
The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through F... more The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through FC simulation interpretation.
Global switching on-the-fly trajectory surface hopping molecular dynamics simulation was performe... more Global switching on-the-fly trajectory surface hopping molecular dynamics simulation was performed on the accurate TD-B3LYP/6-31G* potential energy surfaces for E-to-Z and Z-to-E photoisomerization of dMe-OMe-NAIP up to S1(ππ*) excitation.
Potential energy surface profiles for the excited-state hydrogen transfer of 2′-hydroxychalcone i... more Potential energy surface profiles for the excited-state hydrogen transfer of 2′-hydroxychalcone in terms of a complicated conical intersection network from four low-lying singlet electronic states.
Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to... more Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to reveal the photorelaxation pathways of 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS) upon S1 excitation. Within the interwoven networks of five S1/S0 and three T2/T1 conical intersections (CIs), and three S1/T2, one S1/T1 and one S0/T1 intersystem crossings (ISCs), those competing nonadiabatic decay pathways play different roles in trans-to-cis and cis-to-trans processes, respectively. After being excited to the Franck–Condon (FC) region of the S1 state, trans-S1-FC firstly encounters an ultrafast conversion to quinoid form. Subsequently, the relaxation mainly proceeds along the triplet pathway, trans-S1-FC → ISC-S1/T2-trans → CI-T2/T1-trans → ISC-S0/T1-twist → trans- or cis-S0. The singlet relaxation pathway mediated by CI-S1/S0-twist-c is hindered by the prominent energy barrier on S1 surface and by the reason that CI-S1/S0-trans and CI-S1/S0-twist-t are both not energetically accessi...
The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through F... more The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through FC simulation interpretation.
A large amount of complicated reaction networks of intermediates and radicals taken place in the ... more A large amount of complicated reaction networks of intermediates and radicals taken place in the pyrolysis of 2,5-dimethylfuran have been investigated based on the density function theory (DFT) and the sophisticated wave function theory (WFT) methodologies. The preliminary focus is concentrated on those without the furan-ring opening reaction processes. Calculations are performed for electronic structures, stability and electronic spectra of ground states and excited states for those intermediates and radicals. It is found that both low-lying valence excited states and Rydberg states (3s, 3px, 3py and 3pz) of the pyrolytic species might be involved in pyrolysis and combustion of 2,5-dimethylfuran and influence their chemical reaction kinetics. A generous tendency is also found that the vertical transition energies of the similar transitions become bigger with the removal of methyl in the furan ring.
ABSTRACT Recent rapid progress in quantum chemical calculations has made it possible to perform t... more ABSTRACT Recent rapid progress in quantum chemical calculations has made it possible to perform the first principle calculations of various molecular spectroscopies and photophysical processes. Anharmonic effect on molecular electronic absorption and luminescence like fluorescence and phosphorescence spectroscopies and electronic relaxation processes like internal conversion and intersystem crossing has been theoretically developed 10 years ago. This chapter reviews its applications to pyridine, pyrimdine, pyrazine, and fluorobenzene. It then presents the molecular theories of all types of sum-frequency generation (SFG) including both vibrational SFG (VSFG) and electronic SFG (ESFG). A couple of SFG examples based on the quantum chemical calculations are included for demonstration. The chapter presents how to perform the calculations of the intramolecular vibrational redistribution (IVR) for water clusters and amino acid molecules and their peptides. It applies the femto-second (fs) time-resolved density matrix method to treat the Bixon–Jortner (B-J) model which is a popular method for studying photophysical process.
Recently, the Landau-Zener-Stueckelberg problems have been completely solved in a form convenient... more Recently, the Landau-Zener-Stueckelberg problems have been completely solved in a form convenient for various applications. A summary of the results will be reported. Other related subjects such as multi-level curve crossing and conical intersection problems will also be briefly touched upon.
The density matrix method is a powerful theoretical technique to describe the ultrafast processes... more The density matrix method is a powerful theoretical technique to describe the ultrafast processes and to analyze the femtosecond time-resolved spectra in the pump-probe experiment. The dynamics of population and coherence of the system can be described by the evolution of density matrix elements. In this chapter, the applications of density matrix method on internal conversion and vibrational relaxation processes will be presented. As an example, the ultrafast internal conversion process of ππ* → nπ* transition of pyrazine will be presented, in which case the conical intersection is commonly believed to play an important role. A treatment with Q-dependent nonadiabatic coupling will be applied to deal with the internal conversion rate. Another important ultrafast process, vibrational relaxation, which usually takes place in sub-ps and ps range, will be treated using adiabatic approximation. Then the vibrational relaxation in water dimer and aniline will be chosen to demonstrate the c...
The emission spectra of triphenylamine salicylaldehyde derivatives are weak in solution and stron... more The emission spectra of triphenylamine salicylaldehyde derivatives are weak in solution and strong in the crystal, as interpreted by molecular spectral and dynamics simulations.
The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through F... more The excited state dynamics of m-MeOBDI in acidic methanol–water (pH = 0.6) investigated through FC simulation interpretation.
Global switching on-the-fly trajectory surface hopping molecular dynamics simulation was performe... more Global switching on-the-fly trajectory surface hopping molecular dynamics simulation was performed on the accurate TD-B3LYP/6-31G* potential energy surfaces for E-to-Z and Z-to-E photoisomerization of dMe-OMe-NAIP up to S1(ππ*) excitation.
Potential energy surface profiles for the excited-state hydrogen transfer of 2′-hydroxychalcone i... more Potential energy surface profiles for the excited-state hydrogen transfer of 2′-hydroxychalcone in terms of a complicated conical intersection network from four low-lying singlet electronic states.
Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to... more Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to reveal the photorelaxation pathways of 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS) upon S1 excitation. Within the interwoven networks of five S1/S0 and three T2/T1 conical intersections (CIs), and three S1/T2, one S1/T1 and one S0/T1 intersystem crossings (ISCs), those competing nonadiabatic decay pathways play different roles in trans-to-cis and cis-to-trans processes, respectively. After being excited to the Franck–Condon (FC) region of the S1 state, trans-S1-FC firstly encounters an ultrafast conversion to quinoid form. Subsequently, the relaxation mainly proceeds along the triplet pathway, trans-S1-FC → ISC-S1/T2-trans → CI-T2/T1-trans → ISC-S0/T1-twist → trans- or cis-S0. The singlet relaxation pathway mediated by CI-S1/S0-twist-c is hindered by the prominent energy barrier on S1 surface and by the reason that CI-S1/S0-trans and CI-S1/S0-twist-t are both not energetically accessi...
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