FTIR spectroscopy of uracil derivatives isolated in Kr, Ar and Ne matrices: Matrix effect and Fermi resonance

The vibrational spectra of uracil (2,4-dioxopyrimidine), 1,3-dideuterouracil and 5-methyluracil (thymine) in low temperature Kr, Ar and Ne matrices have been studied by Fourier-transform infrared (FTIR) spectroscopy. The absolute infrared intensities and frequencies of the absorption bands in the infrared (IR) spectra of uracil have been measured. The hypotheses of non-planar conformations of uracil and 5-methyluracil has been tested experimentally. It is shown that the increasing number of spectral bands can be attributed to the Fermi resonance and the matrix splitting. The matrix (Kr, Ar, Ne) effect on fine structure of the absorption bands and Fermi resonance in the IR spectra of uracil, 1,3-dideuterouracil, 5-methyluracil has been studied experimentally.