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SUMMARY:Capturing transient species in ionized liquid water with ultrafast
  x-rays
DTSTART:20191206T110000
DTEND:20191206T120000
DTSTAMP:20260510T062920Z
UID:cf59134017ac4df4ad2d47204896b5efb86a7067d97a4e51cbaf4491
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. Linda Young\nArgonne National Laboratory\, USA  \nUsing u
 ltrafast x-rays to follow the dynamics of chemical reactions in liquid sol
 utions has the potential to place condensed phase reaction dynamics on par
  with understanding in the gas phase.  Here I address a fundamental react
 ion in the solution phase: proton transfer in ionized liquid water.  Ioni
 zation of liquid water is a universal manifestation of the interaction of 
 radiation with matter.  The ensuing cascade of electrons\, ions and radic
 als form the basis of solution and interfacial chemistry in aqueous enviro
 nments in complex systems\, e.g. organisms undergoing medical diagnosis\, 
 radiation therapy\, nuclear reactors and environmental remediation.  I wi
 ll discuss our study of pure water and the initial ultrafast steps of the 
 elementary proton transfer reaction : H2O+ + H2O —›  OH + H3O+\, tri
 ggered by strong-field ionization.  X-rays are uniquely sensitive to two 
 species in the water window\, H2O+ and OH.  By monitoring three photon-in
 /photon-out channels\, x-ray transmission\, total and dispersed x-ray emis
 sion as a function of x-ray photon energy and time delay\,  we find evide
 nce of the elusive H2O+ radical cation as well as a clean and distinctive 
 signature of the OH radical\, complementing earlier studies in the UV.  T
 heoretical studies using a QM/MM approach provide insight into the valence
  hole localization and nuclear dynamics in the water network during the pr
 oton transfer reaction and demonstrate the sensitivity of the x-ray absorp
 tion spectrum to structural dynamics near the reaction center.   The RIX
 S spectrum of the OH radical reveals the complementary nature of x-rays re
 lative to the UV absorption probes.  Interestingly\, the x-ray spectra al
 so show sensitivity to the dynamics of the injected electron. \n\n 
LOCATION:CH G1 495 https://plan.epfl.ch/?room==CH%20G1%20495
STATUS:CONFIRMED
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