Threshold behavior in metastable dissociation of multi-photon ionized thymine and uracil

R. Pandey, M. Ryszka, T. da Fonseca Cunha, M. Lalande, M. Dampc, P. Limão-Vieira, N. J. Mason, J. C. Poully, S. Eden

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8 Citations (Scopus)


Microsecond-timescale HNCO loss has been observed from single-color multi-photon ionized pyrimidine nucleobases in the gas phase. Photon energy thresholds for the metastable channels have been measured at 5.55 ± 0.02 eV for thymine and 5.57 ± 0.02 eV for uracil. We argue that these results can be attributed to accessing the molecules’ S1 states with additional vibrational energy matching the threshold energy for HNCO loss from the radical cation. Combined with previous photoionization energies, this enables the S1 adiabatic energies to be deduced: 3.67 ± 0.07 eV for thymine and 3.77 ± 0.07 eV for uracil. These values are consistent with recent calculations.

Original languageEnglish
Pages (from-to)233-238
Number of pages6
JournalChemical Physics Letters
Publication statusPublished - 1 Jan 2017


  • Mass spectrometry
  • Metastable fragmentation
  • Multi-photon ionization
  • Pyrimidine nucleobases
  • Thymine
  • Uracil


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