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Contribution Oral

X-ray spectroscopy

Resonant interatomic Auger transitions

Speakers

  • Prof. Vladimir GREBENNIKOV

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Co-authors

Content

The interatomic Auger transitions in the presence of core electron levels with close energies are studied theoretically and experimentally. We show that the Coulomb transitions of holes between such levels lead to a resonance (in terms of the energy difference) enhancement of the Auger spectra.

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Figure 1. Diagram of the interatomic Auger process Cu2pCu3pIn4d (a) and Cu2pIn4pIn4d (b) on atoms with interacting internal levels.

Figure 2. The interatomic Auger spectrum Cu2p3pIn4d and the 2pVV copper spectrum in the CuInSe2.

We use the CuInSe2 compound to illustrate our approach. Figure 1 shows a diagram for the amplitude of interatomic Auger transitions Cu2pCu3pIn4d and Cu2pIn4pIn4d. The matrix element of the interatomic Auger transition is usually very small, however, we show that the Coulomb interaction of the levels of neighboring atoms leads to a multiplication of the Auger spectrum intensity (without interaction) by the enhancement factor $$ F = frac{{(W/Gamma)^4}}{{(E 2–E 1)/ Gamma)^2 +1}}. $$ Here W is the matrix element of the Coulomb hole transfer between the states of atoms 1 and 2 (Cu3p and In4p) with energies E1 and E2 and half-width at half maximum of Γ. It is important that the factor F resonantly increases with decreasing energy level difference. The experimental spectrum in Fig. 2, obtained on the Russian-German synchrotron line BESSY-II at photon energies of 1200 and 1210 eV, shows the intense line of the interatomic Auger transition. Binding energies Cu3p3 / 2 eV (75.1 eV) and In4p (73.5 eV) differ by only 1.6 eV, so the half-width Γ 1.5 eV Coulomb transfer holes between levels results in a significant enhancement of the intensity. It can be seen that the Cu2p3 / 23pIn4d spectrum contains three peaks of 830, 838 and 846 eV arising when the orbital angular momenta l = 1 and 2 of the copper and nickel holes are added. A spin-orbit replica of 858, 866 eV also shows the transition originating from Cu2p state with a total angular momentum j = 1/2.

Thus, the resonance enhancement of the cross section at close energy levels on neighboring atoms makes it possible to observe interatomic Auger transitions in the x-ray range.

This work was supported by the RNF (project No. 17-12-01500).