AI Article Synopsis
- The study investigates the ultraviolet absorption spectrum of thiophene using advanced quantum dynamics simulations integrated with a vibronic coupling model.
- The results show strong agreement with experimental data, providing explanations for previously misunderstood spectral features through the interactions of vibrations and coupling between states.
- Analysis reveals that population transfer between states occurs rapidly in less than 100 femtoseconds, while more complex reactions like ring-opening happen over longer timescales, offering a foundation for future research on thiophene's photo-excited dynamics.
Article Abstract
The static gas-phase ("simple") ultraviolet absorption spectrum of thiophene is investigated using a combination of a vibronic coupling model Hamiltonian with multi-configuration time-dependent Hartree quantum dynamics simulations. The model includes five states and all 21 vibrations, with potential surfaces calculated at the complete active space with second-order perturbation level of theory. The model includes terms up to eighth-order to describe the diabatic potentials. The resulting spectrum is in excellent agreement with the experimentally measured spectrum of Holland et al. [Phys. Chem. Chem. Phys. 16, 21629 (2014)]. The, until now not understood, spectral features are assigned, with a combination of strongly coupled vibrations and vibronic coupling between the states giving rise to a progression of triplets on the rising edge of the broad spectrum. The analysis of the underlying dynamics indicates that population transfer between all states takes place on a sub-100 fs timescale, with ring-opening occurring at longer times. The model thus provides a starting point for further investigations into the complicated photo-excited dynamics of this key hetero-aromatic molecule.
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