Quantum Dynamics of the Excited‐State Intramolecular Proton Transfer in 2‐(2′‐Hydroxyphenyl)benzothiazole

The excited‐state intramolecular proton‐transfer dynamics and photoabsorption associated with the ketoenolic tautomerization reaction in 2‐(2′‐hydr oxyphenyl)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.