Relation between copper<i>L</i>x-ray fluorescence and 2<i>p</i>x-ray photoelectron spectroscopies

Abstract

L${\mathrm{\ensuremath{\alpha}}}_{1,2}$,${\mathrm{\ensuremath{\beta}}}_{1}$(${\mathit{L}}_{3,2\mathrm{\ensuremath{-}}}$V) x-ray fluorescence spectra (XRF) and 2${\mathit{p}}_{1/2,3/2}$ x-ray photoelectron spectra (XPS) of various copper compounds are measured. It is found that the intensity of the high-energy hump of the Cu L\ensuremath{\alpha} XRF has a correlation with that of the high-binding-energy satellite (corresponding to the poorly screened 2${\mathit{p}}^{\mathrm{\ensuremath{-}}1}$ final state) of the Cu 2${\mathit{p}}_{3/2}$ XPS. While both the poorly screened peak in the 2${\mathit{p}}_{3/2}$ XPS and the high-energy hump in the L\ensuremath{\alpha} XRF are strong for ionic divalent copper compounds, both of them are very weak for covalent divalent copper compounds, and they exist for neither monovalent nor metallic copper compounds. It was believed that the high-energy hump of the L\ensuremath{\alpha} XRF originated from the electron transition between ${\mathit{L}}_{3}$${\mathit{M}}_{4,5\mathrm{\ensuremath{-}}}$${\mathit{M}}_{4,5}^{2}$ multiple-hole states, where the ${\mathit{L}}_{3}$${\mathit{M}}_{4,5}$ double-hole state was created by the ${\mathit{L}}_{1,2}$${\mathit{L}}_{3}$${\mathit{M}}_{4,5}$ Coster-Kronig transition prior to the x-ray transition. In this context, the L\ensuremath{\alpha} line shape, except for the high-energy hump, was believed to represent the Cu 3d electron density of states (DOS). Our results, however, exclude the possibility of the multiple vacancy satellite 2${\mathit{p}}^{5}$3${\mathit{d}}^{8}$\ensuremath{\rightarrow}3${\mathit{d}}^{7}$ for the origin of the high-energy hump of the L\ensuremath{\alpha} XRF of the divalent copper compounds. It is concluded that the major portion of the high-energy hump of the L\ensuremath{\alpha} XRF of the divalent copper compounds is due to the transition between the poorly screened states 2${\mathit{p}}^{5}$3${\mathit{d}}^{9}$\ensuremath{\rightarrow}3${\mathit{d}}^{8}$. Consequently, it is also concluded that the L\ensuremath{\alpha} line shape does not directly represent the 3d DOS but the high-energy hump hidden in the L\ensuremath{\alpha} main line represents the 3d DOS. We also conclude that the L\ensuremath{\alpha} main line originates from the charge-transfer effect.