Multielectron spectroscopy: Auger decays of the argon 2p hole

All the different Auger decay paths of Argon 2p holes have been characterized using a time of flight spectrometer of the magnetic bottle type. All electrons (the photoelectron and up to three Auger electrons) are detected in coincidence and resolved in energy. Double Auger decay is shown to proceed either through a direct process or by intense cascade paths, implying highly excited autoionizing Ar2+ states, which are identified as Ar2+ 3s−2 correlation satellites. Triple Auger decay is also observed and estimated to account for 0.2% only of all Auger decay

Dynamics of electron emission in double photoionization processes near the Krypton 3d threshold

Two electron emission following photoabsorption near the Kr 3d threshold is investigated both experimentally and theoretically. On the experimental side, electron/electron coincidences using a magnetic bottle time of flight spectrometer allow us to observe the complete Double Photo Ionisation (DPI) continua of selected Kr2+ final states, and to see how these continua are affected by resonant processes in the vicinity of the Kr 3d threshold. The analysis is based on a quantum mechanical approach that takes into account the contribution of three different processes: A) Auger decay of the inner 3d vacancy with the associated post collision interaction (PCI) effects, B) capture of slow photoelectrons into discrete states followed by valence multiplet decay (VMD) of the excited ionic states and C) valence shell DPI. The dominant process for each Kr2+(4p-2) final state is the photoionization of the inner shell followed by Auger decay of the 3d vacancies. Moreover, for the 4p2(3P) and 4p-2(1D) final ionic states an important contribution comes from the processes of slow photoelectron capture followed by VMD as well as from double ionization of the outer shell involving also VMD

Ultrafast charge transfer processes accompanying KLL Auger decay in aqueous KCl solution

X-ray photoelectron spectroscopy (XPS) and KLL Auger spectra of aqueous KCl solution were measured for the K$^+$ and Cl$^-$ edges. While the XPS spectra of potassium and chloride have similar structures, both exhibiting only weak satellite structures near the main line, the Auger spectra of these isoelectronic ions differ dramatically. A very strong satellite peak was found in the K$^+$ KLL Auger spectrum at the low kinetic energy side of the $^1$D state. Using equivalent core models and ab initio calculations this spectral structure was assigned to electron transfer processes from solvent water molecules to the solvated K$^+$ cation. Contrary to the potassium case, no extra peak was found in the KLL Auger spectrum of solvated Cl$^-$ indicating on a strong dependence of the underlying processes on ionic charge. The observed charge transfer processes are suggested to play an important role in charge redistribution following single and multiple core-hole creation in atomic and molecular systems placed into an environment

4d-inner-shell ionization of Xe+ ions and subsequent Auger decay

We have studied Xe+4d inner-shell photoionization in a direct experiment on Xe+ ions, merging an ion and a photon beam and detecting the ejected electrons with a cylindrical mirror analyzer. The measured 4d photoelectron spectrum is compared to the 4d core valence double ionization spectrum of the neutral Xe atom, obtained with a magnetic bottle spectrometer. This multicoincidence experiment gives access to the spectroscopy of the individual Xe2+4d−15p−1 states and to their respective Auger decays, which are found to present a strong selectivity. The experimental results are interpreted with the help of ab initio calculations.1\. Auflag

Разработка рекламной кампании промышленного предприятия и оценка ее эффективности (на примере ОАО «Коминтерн»)

Spectra of triply charged carbon disulphide have been obtained by measuring, in coincidence, all three electrons ejected in its formation by photoionization. Measurements of the CS23+ ion in coincidence with the three electrons identify the energy range where stable trications are formed. A sharp peak in this energy range is identified as the 2Π ground state at 53.1±0.1 eV, which is the lowest electronic state according to ab initio molecular orbital calculations. Triple ionization by the double Auger effect is provisionally divided, on the basis of the pattern of energy sharing between the two Auger electrons into contributions from direct and cascade Auger processes. The spectra from the direct double Auger effect via S 2p, S 2s, and C 1s hole states contain several resolved features and show selectivity based on the initial charge localization and on the identity of the initial state. Triple ionization spectra from single Auger decay of S 2p -based core-valence states CS22+ show retention of the valence holes in this Auger process. Related ion-electron coincidence measurements give the triple ionization yields and the breakdown patterns in triple photoionization at selected photon energies from 90 eV to above the inner shell edges

Reconstruction and control of a time-dependent two-electron wave packet

The concerted motion of two or more bound electrons governs atomic1 and molecular2,3 non-equilibrium processes including chemical reactions, and hence there is much interest in developing a detailed understanding of such electron dynamics in the quantum regime. However, there is no exact solution for the quantumthree-body problem, and as a result even the minimal system of two active electrons and a nucleus is analytically intractable4. This makes experimental measurements of the dynamics of two bound and correlated electrons, as found in the helium atom, an attractive prospect.However, although the motion of single active electrons and holes has been observed with attosecond time resolution5-7, comparable experiments on two-electron motion have so far remained out of reach. Here we showthat a correlated two-electron wave packet can be reconstructed froma 1.2-femtosecondquantumbeatamong low-lying doubly excited states in helium.The beat appears in attosecond transient-absorption spectra5,7-9 measured with unprecedentedly high spectral resolution and in the presence of an intensity-tunable visible laser field.Wetune the coupling10-12 between the two low-lying quantum states by adjusting the visible laser intensity, and use the Fano resonance as a phase-sensitive quantum interferometer13 to achieve coherent control of the two correlated electrons. Given the excellent agreement with large-scalequantum-mechanical calculations for thehelium atom, we anticipate thatmultidimensional spectroscopy experiments of the type we report here will provide benchmark data for testing fundamental few-body quantumdynamics theory in more complex systems. Theymight also provide a route to the site-specificmeasurement and control of metastable electronic transition states that are at the heart of fundamental chemical reactionsWe thank E. Lindroth for calculating the dipole moment (2p2|r|sp2,3+), and also A. Voitkiv, Z.-H. Loh, and R. Moshammer for helpful discussions. We acknowledge financial support by the Max-Planck Research Group Program of the Max-Planck Gesellschaft (MPG) and the European COST Action CM1204 XLIC. L. A. and F. M. acknowledge computer time from the CCC-UAM and Mare Nostrum supercomputer centers and financial support by the European Research Council under the ERC Advanced Grant no. 290853 XCHEM, the Ministerio de Economía y Competitividad projects FIS2010-15127, FIS2013-42002-R and ERA-Chemistry PIM2010EEC-00751, and the European grant MC-ITN CORIN

Butterfly C2H2++: New way for the decomposition of the acetylene dication

International audienceUsing highly correlated ab initio methods, a new transition state is characterized in the lowest singlet potential energy surface of HCCH++. This transition state possesses a dibridged (or "butterfly") form not observed yet for any acetylic compound. It can be reached either directly or after spin-orbit conversion of triplet HCCH++ ions. In light of these calculations, a reaction pathway for the proton pair formation (i.e., HCCH++-> C-2+H++H+) is proposed. (c) 2007 American Institute of Physics

2èmes Journées de Modélisation dans la région parisienne, ENS-ENSCP

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