Direct Femtosecond Observation of Tight and Loose Ion Pairs upon Photoinduced Bimolecular Electron Transfer


  • This research has been supported by the Swiss National Science Foundation (Project Nr. 200020-115942 to E.V.), the European Science Foundation (DYNA travel grant 1267 to O.F.M.), and Laserlab Europe (Project mbi001176 to E.V.).


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Polarization-sensitive ultrafast infrared measurements on photoinduced electron transfer in donor–acceptor pairs in polar acetonitrile show distinct contributions from loose and tight ion pairs. Highly anisotropic signals from tight ion pairs reveal the importance of mutual orientation of the reactants (see picture) and thus the need to refine theoretical models based on spherical species that solely involve reaction distances.