Relaxation of Electronically Excited Hydrogen Peroxide in Liquid Water: Insights from Auger-Electron Emission

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• 作者：Stephan Th眉rmer ; Isaak Unger ; Petr Slav铆膷ek ; Bernd Winter
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 31, 2013
• 年：2013
• 卷：117
• 期：43
• 页码：22268-22275
• 全文大小：382K
• 年卷期：v.117,no.43(October 31, 2013)
• ISSN：1932-7455

文摘

Autoionization electron spectroscopy is applied to study nonradiative relaxation processes of hydrogen peroxide aqueous solution irradiated by soft X-rays. The high kinetic energy part of the oxygen 1s H₂O₂(aq) Auger-electron spectrum reveals dicationic final states with considerably lower energy than for neat liquid water. Assisted by quantum chemical calculations, it is argued that such lower-energy states arise from two fundamentally different relaxation processes. One is (local) Auger decay, yielding H₂O₂²⁺(aq) species, and here the low final-state energy arises from charge delocalization across the molecular O鈥揙 bond. Alternatively, nonlocal dicationic states can form, corresponding to a charge-separated complex comprising H₂O₂ and a neighboring water molecule. Different charge-separation mechanisms, depending on whether or not proton dynamics of the core-level excited or ionized H₂O₂ molecule is involved, are discussed. We also present for the first time the partial electron yield X-ray absorption spectrum of liquid water, which is useful in interpreting the respective spectra from H₂O₂ in water, especially when identifying solute-specific excitations.