The excited-state intramolecular proton-transfer dynamics and photoabsorption associated with the ketoenolic tautomerization reaction in 2-(2'-hydroxyphenyl)benzothiazole are simulated according to a numerically exact quantum-dynamics propagation method and a full-dimensional excited-state potential energy surface based on an ab initio reaction surface Hamiltonian. The simulations involve the propagation of 69-dimensional wave packets according to the matching-pursuit/split-operator Fourier transform (MP/SOFT) method (Wu, Y.; Batista, V. S. J. Chem. Phys. 2004, 121, 1676-1686). The underlying propagation scheme recursively applies the time-evolution operator as defined by the Trotter expansion to second-order accuracy in dynamically adaptive coherent-state expansions. Computations of time-dependent survival amplitudes, the time-dependent product population, and photoabsorption linewidths are compared to experimental data. The reported results provide fundamental insight on the nature of the excited-state reaction dynamics and demonstrate the capabilities of the MP/SOFT method as a powerful computational tool to study ultrafast reaction dynamics in polyatomic systems.
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