Anion photoelectron imaging of deprotonated thymine and cytosine

Bradley F. Parsons, Sean M. Sheehan, Terry A. Yen, Daniel M. Neumark, Nadine Wehres, Rainer Weinkauf

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


We report the anion photoelectron spectra of deprotonated thymine and cytosine at 3.496 eV photodetachment energy using velocity-mapped imaging. The photoelectron spectra of both species exhibit bands resulting from detachment transitions between the anion ground state and the ground state of the neutral radical. Franck-Condon simulations identify the anion isomers that contribute to the observed photoelectron spectrum. For both thymine and cytosine, the photoelectron spectra are consistent with anions formed by removal of a proton from the N atom that normally attaches to the sugar in the nucleotide (N1). For deprotonated thymine, the photoelectron spectrum shows a band due to a ring breathing vibration excited during the photodetachment transition. The electron affinity for the dehydrogenated thymine radical is determined as 3.250 ± 0.015 eV. For deprotonated cytosine, the photoelectron spectrum lacks any resolved structure and the electron affinity of the dehydrogenated cytosine radical is determined to be 3.037 ± 0.015 eV. By combining the electron affinity with previously measured gas phase acidities of thymine and cytosine, we determine the bond dissociation energy for the N-H bond that is broken.

Original languageEnglish (US)
Pages (from-to)3291-3297
Number of pages7
JournalPhysical Chemistry Chemical Physics
Issue number25
StatePublished - 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


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