Origin of the magic numbers of water clusters with an excess electron

Electron-bound water clusters [e ^-(H ₂O) _n] show very strong peaks in mass spectra for n=2, 6, 7, and (11), which are called magic numbers. The origin of the magic numbers has been an enigma for the last two decades. Although the magic numbers have often been conjectured to arise from the intrinsic properties of electron-bound water clusters, we attributed them not to their intrinsic properties but to the particularly weak stability of the corresponding neutral water clusters (H ₂O) _{n=2,6,7, and (11)}. As the cluster size increases; this nonsmooth characteristic feature in stability of neutral water clusters is contrasted to the smooth increase in stability of e ^--water clusters. As the magic number clusters have significant positive adiabatic electron affinities, their abundant distributions in atmosphere could play a significant role in atmospheric thermodynamics.