Study of the Excited States of the Lnner Core Levels in Rare-Earth Compounds

Research Project

Project/Area Number	60540214
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	固体物性
Research Institution	College of Engineering, University of Osaka Prefecture
Principal Investigator	AITA Osamu College of Engineering, Univ. of Osaka Pref, 工学部, 助教授 (30006457)
Co-Investigator(Kenkyū-buntansha)	KAMADA Masao College of Engineering, Univ. of Osaka Pref, 工学部, 助手 (60112538) OKUSAWA Makoto College of Engineering, Univ. of Osaka Pref, 工学部, 助手 (50112537)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥1,500,000 (Direct Cost: ¥1,500,000) Fiscal Year 1986: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1985: ¥900,000 (Direct Cost: ¥900,000)
Keywords	Resonant emission / Valence fluctuation / 等色X線
Research Abstract	The electronic property of rare-earth compounds containing a partially filled 4f shell has been a subject of theoretical and experimental studies because the rare-earth ions in some of these substances are in a homogeneous mixed-valence state. In the present study we measured the rare-earth <M_(4,5)> emission spectra of some rare-earth hexaborides( <CeB_6> , <NdB_6> , and <SmB_6> ) with near-thrshold electron excitation method to elucidate the electronic structure of these substances. The characteristic isochromat spectra and the continuum limit spectra were also measured for this purpose. The results are summarized as follows: 1. The positions of the peaks in the rare-earth <M_(4.5)> emission spectra of these substances clearly coincide with those of the absorption peaks. Therefore, the emission peaks are interpreted as the resonant emissions caused by the transition 3 <d^9> 4 <f^(n+1)> 3 <d^(10)> 4 <f^n> , where n equals the number of the 4f electrons in the ground state. The Sm <M_(4 … More ,5)> emission and characteristic isochromat spectra of Sm <B_6> show no distinct indication of the spectrum corresponding to the <Sm^(2+)> ion regardless of the valence mixing of this substance. 2. The characteristic isochromat spectra at the photon energy of the resonant peak exhibit that the electron-beam energy beyond the energy of the resonant peak is required for the generation of the resonant emission(3 <d^9> 4 <f(n+1)> 3 <d^(10)> 4 <f^n> ). This is ascribed to the formation of the transient state 3 <d^9> 4 <f^(n+2)> , which is caused by both the electron excited from the 3d level and the incident electron losing the initial energy. 3. The rare-earth <N_(4,5)> absorption spectra of some rare-earth compounds were also measured. The Sm <N_(4,5)> absorption spectrum of Sm <B_6> shows no distinct indication due to the <Sm^(2+)> ion. 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 4d ionization threshold of the <Sm^(2+)> ion. Less