Undercoordination induced quantum entrapment and polarization.^{[31,63,64,67,68]} (a) The O 1s energy shifts from the bulk value of 536.6 eV to 538.1 eV for the skin and to 549.7 eV for gaseous state. (b) The hydrated nonbonding electron shifts its energy from the core value of 2.4 eV and the skin of 1.2 eV to the limit of 0.4 eV for N = 5 cluster. Inset (b) shows the cluster size dependent ω_H blueshift.^[4]