Auger Electron Spectroscopy as a Probe of the Solution of Aqueous Ions

Pokapanich, Wandared; Bergersen, Henrik; Bradeanu, I. L.; Marinho, Ricardo R. T.; Lindblad, Andreas; Legendre, Sébastien; Rosso, Aldana; Svensson, S.; Björneholm, Olle; Tchaplyguine, Maxim; Öhrwall, Gunnar; Kryzhevoi, Nikolai V.; Cederbaum, Lorenz S.

doi:10.1021/ja8096866

Cited by 34 publications

(52 citation statements)

References 37 publications

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“…Importantly, the corresponding CT processes involve solvent water molecules which donate their electrons to the solute and thus gets ionized in the end. We also note that in contrast to ICD peaks appearing at the high kinetic energy side of Auger peaks [18,25], the CT peak observed in the present study has lower kinetic energy than the Auger peak. Thus, ICD and CT processes can be distinguished spectroscopically.…”

Section: Introductioncontrasting

confidence: 57%

“…Large relaxation of valence electrons induced by creation of two 2p core holes in the KLL Auger decay seems to play a decisive role in the CT processes. Note that CT processes accompany neither the LMM Auger decay in K + (aq) and Ca 2+ (aq) [18,25] nor the KLL Auger decay in solvated Na + [37]. The corresponding Auger processes create outer-valence double vacancies and do not lead to strong electron reorganization in the valence shell.…”

Section: Discussionmentioning

confidence: 98%

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Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution

et al. 2017

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X-ray photoelectron spectroscopy (XPS) and KLL Auger spectra of aqueous KCl solution were measured for the K + and Cledges. 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.Charge transfer (CT) processes and related phenomena are topics of wide relevance in chemistry, physics and biology. They are responsible for numerous important transformations in living organisms and are involved in fundamental steps describing, e.g., the photosynthesis [1] and respiration [2] mechanisms. The creation of a charge (or hole) in a DNA chain, by oxidation or photoionization processes, is quickly followed by its migration along portions of the molecular backbone leading to possible bonds breaking and irreversible damages [3]. Naturally, the use of such very fast elemental processes for technological purposes has attracted an extraordinary large amount of scientists whose research programs -both theoretical and experimental -focus on energy conversion based for instance on photovoltaic or optoelectronic devices [see e.g. ref. [4]].CT may accompany core-hole creation in atoms and molecules which have neighbors, and the corresponding spectral signatures are manifested in XPS spectra as lowenergy CT satellites. Particularly strong CT screening satellites were found in XPS spectra of weak chemisorption systems [5,6], in crystals [7,8], in weakly bound atomic [9] and microsolvated [10][11][12] clusters. As shown in the latter studies, the energy positions and intensities of CT satellites are sensitive to cluster geometries. Furthermore, the type and number of neighbors have strong effects on CT states [13]. CT processes from core-excited metal ions to solvent molecules may quench radiative relaxation processes as observed in fluorescence-yield spectra [14].For elements from the first rows of the periodic table, electronic Auger decay is the main relaxation channel of core-hole states. Core-hole lifetime ranging usually in the femtosecond and sub-femtosecond timescales may serve as an internal reference clock. Using this reference and the relative intensities of spectral peaks, the core-hole clock method allows one to determine timescales of various processes competing to Auger decay, in particular ...

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Section: Introductioncontrasting

confidence: 57%

Section: Discussionmentioning

confidence: 98%

Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution

et al. 2017

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“…Thus, a 2p-electron of Mg may fill the 1s-vacancy and transfer its energy not to another 2p-electron, which would result in the Auger process on the metal, but to a valence electron on water ionising it in a core ICD-like process [20,24,25]. This decay leads to population of Mg…”

Section: 2mentioning

confidence: 99%

The role of metal ions in X-ray-induced photochemistry

2016

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Metal ions play numerous important roles in biological systems being central to the function of biomolecules. In this letter we show that the absorption of X-rays by these ions leads to a complicated chain of ultrafast relaxation steps resulting in the complete degradation of their nearest environment. We conducted high quality ab initio studies on microsolvated Mg 2+ clusters demonstrating that ionisation of an 1s-electron of Mg leads to a complicated electronic cascade comprising both intra-and intermolecular steps and lasting only a few hundreds femtoseconds.The metal cation reverts to its original charge state at the end of the cascade, while the nearest solvation shell becomes multiply ionised and large concentrations of radical and slow electron species build up in the metal's vicinity. We conclude that such cascades involving metal ions are essential for understanding the radiation chemistry of solutions and radiation damage to metal containing biomolecules.

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“…21 More recently ICD-like processes have also been observed for core-ionization and core-excitation of aqueous solutions. 20,[22][23][24][25][26] The coreionization induced processes of ICD type have been also observed and thoroughly discussed for water [27][28] and ammonia clusters. 29 An important difference between relaxation of coreholes and inner-valence holes is that single core-ionization energies are greater than the 3 lowest valence double-ionization energies; thus the Auger channel is always open upon coreionization whereas it might be energetically forbidden upon inner-valence ionization.…”

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On the nature and origin of dicationic, charge-separated species formed in liquid water on X-ray irradiation

et al. 2013

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Identifying the initial products of the interaction of high-energy radiation with liquidwater is essential for understanding the yield and patterns of damage in aqueous condensed matter, including biological systems. Up until now several fast reactions induced by energetic particles in water could not be observed on their characteristic timescales, and hence some of the reaction intermediates involved, particularly those requiring nuclear motion, have not been considered in describing radiation chemistry.Here, through a combined experimental and theoretical study, we elucidate the ultrafast proton dynamics in the first few femtoseconds after X-ray core-level ionization of liquid water. We show through isotope analysis of the Auger-spectra that proton-transfer dynamics occurs on the same timescale as electron autoionization. Proton transfer leads to formation of a Zundel-type intermediate [HO*··H··OH 2 ] + , which further ionizes, forming a so-far unnoticed type of di-cationic, charge-separated species with high internal energy. We call the process proton-transfer mediated charge separation.The primary processes in water initiated by X-radiation are poorly understood despite their paramount importance in different fields. Understanding the energy and charge redistribution in water upon X-ray photon absorption is vital for a design of more efficient radio-oncology schemes, 1-2 for disentangling the physical basis of genotoxic effects on living tissues, [3][4][5] for minimizing the damage of biological samples during X-ray diffraction 2 experiments, 6 as well as for controlling the performance of nuclear reactors under operating conditions. 7 Current understanding of electron-initiated processes in aqueous systems, following energy deposition, and the subsequent radical chemistry have been recently reviewed. 8 An explicit consideration of radicals and molecular species formed via multiple ionization processes of water, involving for instance atomic oxygen and hydrogen peroxide, can be found in the radiolysis literature, e.g. in refs. 7,9 However, the knowledge of the ultrafast processes and mechanisms in water radiolysis remains to large extent unexplored.In the present work we focus on the processes following O1s core-level ionization of water. The highly excited species formed by the core ionization relaxes primarily via Augerelectron decay. As shown in Figure 1b, Auger decay of a water molecule involves refilling the water core-hole by one of the valence electrons, and the simultaneous emission of another valence electron, the Auger electron, from the same water molecule. The resulting highly reactive doubly ionized H 2 O 2+ (aq) molecule, with both vacancies (holes) located at the same site (denoted here as 2h state), then undergoes ultrafast Coulomb explosion, forming dominantly O + 2H + . [10][11] In recent years a set of novel non-local autoionization processes has been identified to play an important role in weakly bonded atomic and molecular systems. [12][13][14] One such relaxation process is Intermolecu...

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Auger Electron Spectroscopy as a Probe of the Solution of Aqueous Ions

Cited by 34 publications

References 37 publications

Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution

Ultrafast Charge Transfer Processes Accompanying KLL Auger Decay in Aqueous KCl Solution

The role of metal ions in X-ray-induced photochemistry

On the nature and origin of dicationic, charge-separated species formed in liquid water on X-ray irradiation

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