Evidence for ultra-fast dissociation of molecular water from resonant Auger spectroscopy

Hjelte, I.; Piancastelli, M. N.; Fink, Reinhold F.; Björneholm, Olle; Bäßler, M.; Feifel, Raimund; Giertz, A.; Wang, H.; Wiesner, Karoline; Ausmees, A.; Miron, Catalin; Sorensen, S. L.; Svensson, S.

doi:10.1016/s0009-2614(00)01434-2

Cited by 118 publications

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“…The term 'mediated' and the corresponding acronym PTM account for the fact that some of the processes considered here are possible only if proton transfer had taken place. These processes occur on the timescale of the oxygen 1s core-hole lifetime (approximately 4 femtoseconds), 30 which is comparable to the 9 fs period of a full O-H vibration in water. Experimentally, we perform a so-called core-hole-clock measurement, [31][32][33] which is based on detecting electron energies emitted by autoionization, occurring continuously from the geometrically evolving manifold of core-ionized structures.…”

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confidence: 99%

“…[34][35][36]39 In the present study, we use Auger spectroscopy for the experimental identification of nuclear dynamics upon ionization, which is mediated by the solvent; gasphase water does not dissociate upon O1s ionization, but it does upon excitation. 30 The dynamics of molecular water upon core-level ionization and excitation has been followed in detail by classical simulations. 47 These authors corroborate the importance of O-H bond lengthening for explaining the part of the spectrum designated as peak 2.…”

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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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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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“…The quadruply charged BF 4þ 3 molecular parent ion can be produced by the multiple Auger decay of the inner-shell excited or ionized states of BF 3 . This channel is very weak, representing less than 1% of the total ionization yield.…”

Section: Multiple-ion Coincidence Momentum Imagingmentioning

confidence: 99%

“…The lifetime of the core-excited state for light atoms such as B, C, N, O and F is of the order of 10 À15 s, i.e., femtoseconds (fs). Within this short time scale, however, nuclear motion of the molecule proceeds in the core-excited state in competition with the Auger decay [1][2][3][4].…”

Section: Introductionmentioning

confidence: 99%

“…We expect the vibrational frequencies of these modes to change slightly from the ground state of the neutral to the core-ionized and core-to-Rydberg excited states of BF 3 , due to the non-bonding character of the orbitals involved. Since m 3 and m 4 do not play a role in the present study, we consider only the m 1 and m 2 modes ðv 1 ; v 2 Þ throughout this paper unless indicated.…”

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