H-atom detachment photochemistry of (hetero)aromatic molecules: ab initio quantum dynamics studies
Final Report Abstract
We have performed computational studies of molecular photodissociation reactions which proceed via conical intersections. The analysis is based on numerically exact quantum dynamical wave-packet calculations for appropriately constructed multi-state multi-mode model Hamiltonians. In addition to rigorous dynamics simulations for these models, computationally efficient approximate methods were developed and their performance was illustrated in comparison with the exact calculations. The effect of an intermediate conical intersection on the vibrational state distributions of the photofragments was investigated in detail for the example of the ozone molecule. A substantial part of the work of this project was the construction of a full-dimensional (24D) three-sheeted diabatic potential-energy surface for pyrrole. Reduced-dimensional (6D, 11D, 15D) quantum dynamics calculations were performed to simulate the absorption profile of pyrrole and to calculate vibrational state distributions of the pyrrolyl radical. These are the first quantum dynamical calculations of vibrationally resolved photofragment distributions of an aromatic molecule. The calculated H-atom kinetic-energy spectra were compared with experimental data and the results were interpreted in terms of the topography of the PE surfaces. The photodissociation dynamics of the pyridinyl radical was studied in the framework of an ab initio based three-state three-mode model. While this model has limitations due to the restricted number of electronic states and vibrational modes, this work represents the first theoretical investigation of the photodissociation dynamics of a hypervalent aromatic radical.
Publications
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(2018) Photodissociation dynamics in the first absorption band of pyrrole. I. Molecular Hamiltonian and the Herzberg-Teller absorption spectrum for the A21(πσ*)←X̃1 A1(ππ) transition. The Journal of chemical physics 148 (10) 104103
Picconi, David; Grebenshchikov, Sergy Yu
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(2018) Photodissociation dynamics in the first absorption band of pyrrole. II. Photofragment distributions for the 1 A 2 (π σ*)← X ̃ 1 A 1 (π π) transition. The Journal of Chemical Physics 148 (10) 104104
D. Picconi and S. Yu. Grebenshchikov
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Signatures of conical intersections in photofragment distributions and absorption spectra: Photodissociation in the Hartley band of ozone. J. Chem. Phys. 141, 074311 (2014)
D. Picconi and S. Yu. Grebenshchikov
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Intermediate photofragment distributions as probes of nonadiabatic dynamics at conical intersections: Application to the Hartley band of ozone. Phys. Chem. Chem. Phys. 17, 28931 (2015)
D. Picconi and S. Yu. Grebenshchikov
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Partial dissociative emission cross sections and product state distributions of the resulting photofragments. Chem. Phys. 481, 231 (2016)
D. Picconi and S. Yu. Grebenshchikov
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Fano resonances in the photoinduced H-atom elimination dynamics in the πσ* states of pyrrole. Phys. Chem. Chem. Phys. 19, 14902 (2017)
S. Yu. Grebenshchikov and D. Picconi
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Photodissociation dynamics of the pyridinyl radical: Time-dependent quantum wavepacket calculations. J. Chem. Phys. 146, 124304 (2017)
J. Ehrmaier, D. Picconi, T. N. V. Karsili and W. Domcke
