Postcollision-interaction effects in multistep Auger transitions following Ar 1s photoionization (original) (raw)
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PCI effects in argon 2p double Auger decay probed by multielectron coincidence methods
Journal of Physics B: Atomic, Molecular and Optical Physics, 2010
Electron correlations in three electron emission associated with innershell photoionization are investigated for the first time through a combined theoretical and experimental approach. Namely, different kinds of Post Collisional Interactions (PCI) occurring in the decay of Argon 2p holes by emission of two Auger electrons are isolated experimentally with a powerful coincidence technique and are modeled with an eikonal approach. It is shown that PCI distortion of the photoelectron line shape is stronger than in the single Auger paths and depends critically on the process: in direct Double Auger decays where two Auger electrons are emitted simultaneously, direct interaction of the 2p photoelectron with the two Auger electrons is demonstrated; in cascade Double Auger processes, the PCI distortion depends only slightly on the last electron emitted in the cascade. This perturbation depends on and reveals the lifetime of the intermediate Ar 2+ state.
Photoion Auger-electron coincidence measurements near threshold
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1991
The vacancy cascade which fills an atomic inner-shell hole is a complex process which can proceed by a variety of paths, often resulting in a broad distribution of photoion charge states. We have measured simplified argon photoion charge distributions by requiring a coincidence with a K-LL or K-LM Auger electron, following K excitation with synchrotron radiation, as a function of photon energy, and report here in detail the argon charge distributions coincident with K-L1L23 Auger electrons. The distributions exhibit a much more pronounced photon-energy dependence than do the more complicated non-coincident spectra. Resonant excitation of the K electron to np levels, shakeofF of these np electrons by subsequent decay processes, double-Auger decay, and recapture of the K photoelectron through postcollision interaction occur with significant probability.
Argon 1s photoionization followed by multiple Auger decays is investigated both experimentally, by means of photoelectron-ion coincidences, and theoretically. A strong influence of the different Auger decays on the photoelectron spectra is observed through postcollision interaction which shifts the maximum of the energy distribution and distorts the spectral shape. A good agreement between the calculated and measured spectra for selected Ar nþ ions (n ¼ 1–5) allows one to estimate the widths (lifetimes) of the intermediate states for each specific decay pathway.
Electron–electron coincidence study of double Auger processes in atoms
Journal of Electron Spectroscopy and Related Phenomena, 2004
The double Auger process after Ar 2p and Ne 1s inner-shell photoionization is investigated by means of angle resolved time-of-flight electronelectron coincidence spectroscopy. This method allows to disentangle direct double Auger from cascade Auger processes. Information about the energy sharing as well as the angular correlation of the two emitted electrons is obtained. Circular dichroism in the double Auger emission produced by circularly polarized light is discussed.
Fluorescence Time Delay in Multistep Auger Decay as an Internal Clock
Physical Review Letters, 2020
Differences in postcollision interaction (PCI) effects on Kr L 3 M 4;5 M 4;5 Auger electron spectra were observed, depending on whether the initial photoionization occurred slightly above the K threshold or slightly above the L 3 threshold. For the former, KL fluorescence emission most likely happens and then Auger processes due to the L 3 hole follow. The time delay due to fluorescence causes a reduced shift of the Auger peak and tailing toward lower energy, since the Auger overtaking of the photoelectron happens later in time and at a location farther away from the ionic core, compared to the case for the simple one-step L 3 M 4;5 M 4;5 Auger decay after L-shell photoionization. Time-dependent theory for PCI in multistep processes agrees well with experiment, illustrating the effect as an internal clock for the time-sequence of the dynamical process.
Study of second-step Auger transitions in Auger cascades following 1s → 3p photoexcitation in Ne
Journal of Physics B: Atomic, Molecular and Optical Physics, 2005
We present the results of high-resolution measurements of the low-energy part of the Auger electron spectrum generated by photoexcitation of the 1s −1 3p resonance in Ne. The spectrum was measured in the energy range of 10-33 eV where mainly the electrons from the second-step Auger transitions of the cascades 1s −1 3p → 2s2p 5 np → 2s 2 2p 4 and 1s −1 3p → 2s 0 2p 6 np → 2s2p 5 (n = 3, 4) are detected. High resolution allows us to study the multiplet structure of the transitions and to determine the widths of the intermediate states of the Ne + ion. Anisotropy of the angular distribution of Auger electrons is determined for all of the lines observed. The results are in reasonably good agreement with MCDF calculations.
Journal of Electron Spectroscopy and Related Phenomena, 1997
The Ar L 2,3 -MM Auger spectrum induced by impact of 2.0 keV electrons was measured with high resolution (68 Ϯ 4 meV) in the 15-90Њ angular region. Relative yields, level widths and transition energies have been determined for the diagram Auger lines originating from the 2 P 1=2 and 2 P 3=2 initial vacancy states. The data are compared with those of earlier experimental studies and theoretical calculations, including multiconfiguration Hartree-Fock calculations performed in this work. The isotropy of the studied lines has been confirmed. The measured relative intensities of the fine-structure components of the L 23 -MM ( 3 P 0, 1, 2 ) Auger triplets have been found different from those obtained in theoretical calculations and earlier experiments. ᭧ 1997 Elsevier Science B.V.