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Quantum equilibration of the double-proton transfer in a model system porphine.

G. Albareda, A. Riera, M. González, J. M. Bofill, I. P. R. Moreira, R. Valero, I. Tavernelli.
Phys. Chem. Chem. Phys.,22 (2020) 22332.

Two-proton probability density at four representative time values. The initially well-localized nuclear density gives way later to a strong proton delocalization along the synchronous pathway that is maintained for at least 1 ps.

There is a renewed interest in the derivation of statistical mechanics from the dynamics of closed quantum systems. A central part of this program is to understand how closed quantum systems initialized far-from-equilibrium can share a dynamics that is typical to the relaxation towards thermal equilibrium. We consider here the equilibration of a two-dimensional model describing the double proton transfer reaction in porphine. From quantum dynamics simulations it comes out that equilibration takes place very rapidly (∼200 fs) for initial states with energies well above the synchronous barrier. The resulting equilibration state shows a strong delocalization of the protons probability density which arises from: (i) an initial state consisting of a large superposition of vibrational states; (ii) the presence of a very effective dephasing mechanism. This work, which involves two groups of IQTC and was led by Dr. Guillem Albareda, was selected as “2020 PCCP Hot Article”.