title: Bending Vibration-Governed Solvation Dynamics of an Excess Electron in Liquid Acetonitrile Revealed by Ab Initio Molecular Dynamics Simulation.
abstract: We report an ab initio molecular dynamics simulation study of the solvation and dynamics of an excess electron in liquid acetonitrile (ACN). Four families of states are observed: a diffusely solvated state and three ACN core-localized states with monomer core, quasi-dimer (π*-Rydberg mode) core, and dual-core/dimer core (a coupled dual-core). These core localized states cannot be simply described as the corresponding anions because only a part of the excess electron resides in the core molecule(s). The quasi-dimer core state actually is a mixture that features cooperative excess electron capture by the π* and Rydberg orbitals of two ACNs. Well-defined dimer anion and solvated electron cavity were not observed in the 5-10 ps simulations, which may be attributed to slow dynamics of the formation of the dimer anion and difficulty of the formation of a cavity in such a fluxional medium. All of the above observed states have near-IR absorptions and thus can be regarded as the solvated electron states but with different structures, which can interpret the experimentally observed IR band. These states undergo continuous conversions via a combination of long-lasting breathing oscillation and core switching, characterized by highly cooperative oscillations of the electron cloud volume and vertical detachment energy. The quasi-dimer core and diffusely solvated states dominate the time evolution, with the monomer core and dual-core/dimer core states occurring occasionally during the breathing and core switching processes, respectively. All these oscillations and core switchings are governed by a combination of the electron-impacted bending vibration of the core ACN molecule(s) and thermal fluctuations.
authors.affiliation: School of Chemistry and Chemical Engineering, Shandong University , Jinan, 250100 Shandong, P. R. China.
authors.forename: Jinxiang
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, 48824 Michigan, United States.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Cukier
authors.affiliation: School of Chemistry and Chemical Engineering, Shandong University , Jinan, 250100 Shandong, P. R. China.
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Bu