The nature of a floating electron

Dynamics of electron solvation at the water surface is studied using extensive ab initio simulations. Calculations have been performed on semi-classical water at 300 K temperature with an excess quantum electron on its surface. It is found that after a very fast 30–50 fs initial localization, there follow fast 50–70 fs rotationally mediated transitions of the excess electron between surface trap states with a lifetime of 150–400 fs. In less then 2 ps the excess electron gets trapped in an ordered “floating” electron state on the surface of water with a lifetime of more than 7 ps. The excess electron diffusion coefficient and spectrum of its velocity autocorrelation function change over time to reflect a transition from a very mobile phase (first 2 ps) to a trapped “floating” electron phase (2–7 ps).