Argon KLL Auger spectrum: Initial states, core-hole lifetimes, shake, and knock-down processes

Abstract

State-of-the-art Argon KLL Auger spectra measured using photon energies of hν = 3216 eV and 3400 eV are presented along with an Ar [1s] photoelectron spectrum (squared brackets indicate holes in the respective orbital). The two different photon energies used for measuring the Auger spectra allow distinguishing between the shake transitions during the Auger decay and the Auger transitions of the photoelectron satellites. A complete assignment of satellite transitions is provided, partially baseed on configuration interaction calculations. In addition, Artransitions are observed, which can be explained by knock-down transitions leading to a direct exchange of angular momenta between the excited electron and the Auger electron. The lifetime broadenings of the Ar [2s] single core-hole state and the [2s 2 ] as well as [2s2p] double core-hole states are also determined, confirming previously observed trends for double core-hole states.

Experimental and theoretical study of the Kr L -shell Auger decay

“…In the binding-energy region of ∼ = 222 to 234 eV of the L 3 decays there is also some intensity which is not reproduced by theory. These spectral features can be assigned to the Auger decays of shake-up states during the photoionization process, which are expected to be much closer to the main line than the shake satellites originating during the Auger decay [14,15]. This is in line with the discussion of the Auger decay of the 2p −1 3/2 4(s, p) −1 states as will be discussed further below; see Fig.…”

“…In particular, the strongest 4p 6 → 4p 5 5p shake-up transitions are expected, based on the corresponding excitation energies of the Z + 2 atom Sr III about 28 eV [39] above the binding energy of the corresponding diagram line. Such shake-up transitions during the Auger decay have been observed in the Ar KLL [14] and the Xe L 2,3 M 4,5 N 4,5 [31] Auger spectra. In the binding-energy region of ∼ = 222 to 234 eV of the L 3 decays there is also some intensity which is not reproduced by theory.…”

“…We expect that this energy value is too low to observe fully developed shake-off satellites. Finally, we want to mention that for Ar the 1s −1 3p −1 → 2p −2 3p −1 Auger transitions of the dication overlap with the 1s −1 3p −1 np → 2p −2 3p −1 mp transitions of the cation [14]. We expect a similar behavior for krypton, i.e., contributions of the Auger decays of the 2p −1 3/2 4(s, p) −1 n(s, p) states in the region of peaks 1 to 5.…”

“…In addition to this variety of new and interesting effects, the recent instrumental improvements provide also an excellent opportunity to revisit fundamental processes such as Auger decays of deep core holes and study them in unforeseen detail. For example, recent studies of the KLL Auger spectra of atomic argon [14] and sulfur in H 2 S [15] provided de-tailed information about the satellite structure. In particular, both studies demonstrated that shake processes during the Auger decay cannot be neglected although they were completely ignored in previous studies; note that for these studies tunable photon energies were very essential.…”

“…In addition, for Ar 1s −1 3l −1 nl 1 → 2p −2 ( 1 D 2 , 1 S 0 ) Auger satellites were observed. A detailed investigation showed that these transitions can only be explained by the knock-down effect since an angular-momentum transfer between the outgoing Auger electron and the excited valence electron is required [14].…”