Fourthly, the polarizability is molecular site and droplet size dependent. One can probe the local polarizability by injecting a free electron into different sites of the droplet without changing the structural geometry . The electron occupies eccentrically the tetrahedral hollo site to form an (e -)⋅4H2O motif like the (Na + )⋅4H2O hydration cell , without exchange interaction. The bound and (b) lifetime of the hydrated electron, (c) H-O phonon frequency shift , and (d) supercooling for ice formation . A droplet of more curved skin takes longer durtion than a less cuved one to freeze at the same temperature .