Energieverlustmessungen an der Legierungsreihe Rhodium-Palladium-Silber

Abstract

Characteristic energy loss spectra of rhodium, palladium, silver and the intermediate solid solutions Rh₅₀Pd₅₀ and Pd₅₀Ag₅₀ were measured in reflection. The electrons primary energy was variied from 200 to 800 eV. The total scattering angle was 45°. The first energy loss ΔE ₁ was found to be the most prominent. Its value is closely related to the position of the Fermi edge in a rigid band model of this alloy series. A comparison with the shift of the Fermi edge from isochromat spectroscopic measurements shows good agreement of ΔE ₁ with$\hbar \omega _{\varepsilon _1 = 0}$. The excitation probabilities of theDE ₁-loss for rhodium and palladium were measured. For primary energiesE}>300 eV they are in good agreement with a formula given byRitchie for surface losses in thick foils. ForE<300eV, the decrease of the probability seems to be a consequence of very small “effective” penetration depths in the concerning metals. TheRitchie formalism for very thin foils can account for our results in this case also. The resulting “effective” penetration depth of about 5 Å forE≈300eV is in good agreement with the magnitude of LEED-measurements.