. . . "http://www.iso.org/iso/catalogue_detail?csnumber=31897"^^ . . . "E_i" . . . . . . . . . . . . . . . . . . "\"Ionization Energy\" is the energy difference between an electron at rest at infinity and an electron at a certain energy level. The amount of energy required to remove an electron from that atom or molecule in the gas phase." . . . . . . . . . . . . . "http://en.wikipedia.org/wiki/Ionization_energy"^^ . . . . . . . . . "Ionization Energy"@en . . . . . . . .