(a) Absorption spectra of trivalent lanthanides and actinides in the visible region. The distinct differences in the spectra enables precise selection. The green broken line indicates the laser wavelength used for the selective excitation of americium (Am). The color scale represents the molar absorption coefficient (M^-1 cm^-1). (b) Conceptual drawing of the laser-assisted separation, depicting the photoreaction with inner-shell electrons only for Am. Because of the similarity of ion sizes (orange dotted curves), size recognition with ordinary extractants cannot be applied for ion separation. (c) The excitation scheme of resonance-enhanced multiphoton excitation. The first excitation is responsible for the selectivity, and the second excitation, for the reactivity. (d) Change in absorption spectra after laser irradiation and solvent extraction, showing the selective recovery of only photoreacted Am in the aqueous phase.