Abstract UV-light induced intramolecular proton-transfer was observed in matrix isolated 4- oxopyrimidine, 2-pyridone and hypoxanthine. Mixed spectrum of 4-oxo-and 4-hydroxy- pyrimidine in Ar and Ne matrices was unambiguously partitioned into the two sets of peaks corresponding to the two tautomers. Both spectra were compared to the spectra in the solid phases and interpreted.
