Strong4fResonance Effects in Rare-Earth Appearance-Potential Spectra

Abstract

Soft-x-ray appearance-potential spectra of rare-earth elements are interpreted in terms of strong resonance interactions between the incident electrons and atomic 4/ states. These interactions account for both the large intensity and the threshold shifts of the measured signal. This resonance persists in La, Ce, Pr, arid Nd when present as only a few atomic percent in a NiCr alloy reflecting the local character of the interaction.

Application of soft x-ray appearance potential spectroscopy to light lanthanides, 4d transition metals, and insulators

“…Fig. 9 shows a C r L spectrum obtained from t h e , s t a i n l e s s s t e e l substrate used 3,2 i n our work and the C r oxide spectrum of Fig. 8. The agreement of the two curves is nearly exact, both i n energy and l i n e shapes.…”

“…8, 9, and 10. Comparing the two curves of FQ. 8, we see f i r s t , that the L~/ L~ peak-height r a t i o changes from unity f o r the clean material t o about 1.25 f o r the oxide. Also, the 1% shape f o r the oxide spec<mn appears no& symmetric, having l a r g e r negative peaks.…”

“…For most of these 3 m t e r i a l s , however, the agreenent breaks down as one moves abovc threshold. In some of the l i g h t e r elements such as carbon o r boron, new feat u r e s appear i n the spectrum due t o the excitation of collective modes (12,13), and finally, f o r &L (6) and the rare earths (7,8,9,28) the above model fails completely. The spectra f o r the rare earths La, Ce and Yb are presented i n Chapter N of t h i s work, as w e l l as sons typical carbon results.…”

“…b r t e e t a l . (8) current normalization w i l l enhance the N region. Second, the spectrum 4,5 represents a derivative of the t o t a l x-ray fluorescence yield.…”

Appearance Potential Spectroscopy (APS): Old Method, but Applicable to Study of Nano-structures

“…70 The 3d5/2 binding energies of La, Ce, Pr, and Nd were compared with those obtained by XPS and XAS. 72 The SXAPS and AEAPS 3d spectra of La were also compared and the result concluded that bremsstrahlung does not dominate the spectral shape in APS (Fig.…”