title: Tautomerism in cytosine and uracil: an experimental and theoretical core level spectroscopic study.
abstract: The O, N, and C 1s core level photoemission spectra of the nucleobases cytosine and uracil have been measured in the vapor phase, and the results have been interpreted via theoretical calculations. Our calculations accurately predict the relative binding energies of the core level features observed in the experimental photoemission results and provide a full assignment. In agreement with previous work, a single tautomer of uracil is populated at 405 K, giving rise to relatively simple spectra. At 450 K, three tautomers of cytosine, one of which may consist of two rotamers, are identified, and their populations are determined. This resolves inconsistencies between recent laser studies of this molecule in which the rare imino-oxo tautomer was not observed and older microwave spectra in which it was reported.
authors.affiliation: Sincrotrone Trieste, in Area Science Park, I-34012 Basovizza (Trieste), Italy.
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Feyer
authors.forename: Oksana
authors.initials: O
authors.lastname: Plekan
authors.forename: Robert
authors.initials: R
authors.lastname: Richter
authors.forename: Marcello
authors.initials: M
authors.lastname: Coreno
authors.forename: Gemma
authors.initials: G
authors.lastname: Vall-llosera
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Prince
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Trofimov
authors.forename: Irina L
authors.initials: IL
authors.lastname: Zaytseva
authors.forename: Tatyana E
authors.initials: TE
authors.lastname: Moskovskaya
authors.forename: Evgeniy V
authors.initials: EV
authors.lastname: Gromov
authors.forename: Jochen
authors.initials: J
authors.lastname: Schirmer
mesh_terms: D002244:Carbon / Q000737:chemistry; D003596:Cytosine / Q000737:chemistry*; D007536:Isomerism; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D011789:Quantum Theory; D013057:Spectrum Analysis; D013696:Temperature; D014498:Uracil / Q000737:chemistry*
chemical_list: D014498:Uracil; D002244:Carbon; D003596:Cytosine; D009584:Nitrogen; D010100:Oxygen