Rare-Earth N_4,5 Absorption Spectra of Some Rare-Earth Compounds

Abstract

The rare-earth N_4,5 absorption spectra of rare-earth compounds RCl₃ (R=La, Ce, Sm, Eu and Gd) and RB₆ (R=La and Sm) were measured to obtain the information on the excited state 4d⁹4fⁿ⁺¹ of these substances, where n equals the number of the 4f electrons in the ground state. The structures of the absorption spectra are well explained by the multiplet states of the 4d⁹4fⁿ⁺¹ configuration in the final state. The Sm N_4,5 absorption spectrum of SmB₆ shows no distinct indication due to the Sm²⁺ ion regardless of the valence mixing between the Sm²⁺ and Sm³⁺ ions. The absorption structure corresponding to the Sm²⁺ ion may be smeared owing to the autoionization process of the excited state 4d⁹4f⁷ of the Sm²⁺ ion because this state is located above the 4d ionization threshold of the Sm²⁺ ion.