Knowledge Bank

Results of infrared studies of uracil and its $N1,N3$-dideuterated homologue isolated in argon and nitrogen matrices are presented and discussed in terms of normal modes predicted by quantum mechanical calculations .The effects on the spectrum of N-deuteration and of the interaction between the isolated molecule and the matrix are discussed. The quantum mechanical calculations are used to make a resonably reliable first assignment absorption bands to all the normal modes for the matrix-isolated uracil molecule. The wave numbers and relative intensities for the absorption bands for the isolated molecule are related to those reported previously for uracil in the solid phase or in polar solution but differ significantly from them.