Ultrafast demethylation following femtosecond-laser-induced ionization of ethanol dimers

We report the experimental observation of ultrafast demethylation in ethanol dimers following single ionization induced by a 400-nm femtosecond laser field, described by the reaction (C₂H₅OH)₂ + nh̄ω → CH₃ + CH₂O · (C₂H₅OH)H⁺ + e⁻. This demethylation pathway is identified through the detection of the ionic fragment CH₂O · (C₂H₅OH)H⁺, accompanied by the coincident measurement of emitted electron. Analysis of the electron-nuclear joint kinetic energy spectrum reveals multiple diagonal features spaced by the photon energy, showing the essential role of electron-nuclear correlation in the demethylation process. The reaction timescale is determined by introducing a time-delayed 800-nm femtosecond probe pulse, yielding a characteristic time of approximately 0.95 ps. This duration is longer than that observed for demethylation following single ionization of ethanol monomers, highlighting the pronounced influence of intermolecular interactions in the dimeric system.