The Absorption Spectra of Europium Ion in Some Hydrated Salts

The absorption spectra of crystalline EuCl3·6H2O, EuBr3·6H2O, and Eu2(SO4)3·8H2O were photographed at various temperatures in the visible and ultraviolet region of the spectra. The salts were found to have low-lying excited levels at about 300 cm-1, 390 cm-1, 938 cm-1, 970 cm-1 and, perhaps, 430 cm-1, which arose from excited electronic, crystal and vibrational frequencies. These levels are discussed in relation to existing theories of specific heat, magnetic susceptibility, etc., of europium.