d-f and f-f transition bands of praseodymium and samarium ions in silica glasses

d-f and f-f transition bands of Pr and Sm ions in silica glasses have been studied by the absorption, excitation and emission spectra. In particular, Sm-doped silica glasses were treated with different atmospheres around the T_g temperature. The change of the valency state and the transition band shown after the treatments are discussed.