The widely accepted notion that excess charge is located on the surface of ESI nanodroplets is in apparent conflict with the well known tendency of ions such as Na~(+) to maximize charge-solvent interactions by migrating towards the bulk. The MD simulations of this work confirm that charged droplets exhibit ion distributions centered around 2/3 R, where the ion solvation requirements are fully satisfied. Nonetheless, Coulomb energy mapping reveals that all excess charge is confined to a thin layer at the droplet periphery. These seemingly contradictory findings are reconciled on the basis of charge-induced orientation of water dipole moments. Ions in the droplet interior become essentially neutralized through charge-dipole interactions. Orientational polarization of water molecules then acts to transfer the excess charge to the droplet periphery.
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