Rare-Earth N4,5 Absorption Spectra of Some Rare-Earth Compounds

The rare-earth N 4,5 absorption spectra of rare-earth compounds RCl 3 , (R=La, Ce, Sm, Eu and Gd) and RB 6 (R=La and Sm) were measured to obtain the informationon the excited state 4 d 9 4 f n +1 of these substances, where n equals the number of the 4 f electrons in the ground state. The structures of the absorption spectra are well explained by the multiplet states of the 4 d 9 4 f n +1 configuration in the final state. The Sm N 4,5 absorption spectrum of SmB 6 shows no distinct indication due to the Sm 2+ ion regardless of the valence mixing between the Sm 2+ and Sm 3+ ions. The absorption structure corresponding to the Sm 2+ ion may be smeared owing to the autoionization process of the excited state 4 d 9 4 f 7 of the Sm 2+ ion because this state is located above the 4 d ionization threshold of the Sm 2+ ion.