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Electron detachment dynamics of the iodide-guanine cluster: does ionization occur from the iodide or from guanine? does ionization occur from the iodide or from guanine?

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JournalMolecular Physics
DateAccepted/In press - 6 Oct 2019
DateE-pub ahead of print (current) - 20 Oct 2019
Early online date20/10/19
Original languageEnglish

Abstract

Laser photodissociation spectroscopy of the I·guanine complex has been conducted for the first time across the regions above the electron detachment threshold to explore the excited states and whether vertical ionisation occurs from the iodide or the nucleobase. The photofragment spectra reveal a prominent dipole-bound excited state (I) close to the calculated vertical electron detachment energy (∼4.0 eV) and a second excited (II) centred around 4.8 eV, which we assign to π-π* nucleobase-localised transitions. The ionic photofragments are identified as I and I·[G-H], with the later fragment being produced significantly more strongly than the former. Both photofragments are observed across the two excited states, with production of the iodide being attributed to internal conversion to the ground state followed by evaporation. We trace the formation of the I·[G-H] photofragment to initial vertical ionisation of guanine, followed by ejection of a proton. This two-step process is important as it follows known steps in radiation-induced damage to DNA, namely initial formation of a guanine radical cation which then forms a free radical [G-H] moiety through deprotonation. Production of the I·[G-H] photofragment is pronounced through II indicating that its formation is enhanced by coupling of the π-π* transitions to the electron detachment continuum.

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© 2019 Informa UK Limited. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

    Research areas

  • charge transfer, deprotonation, Guanine, photodissociation, radical cation

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