VIBRATIONALLY EXCITED-STATES IN C3V MOLECULES - CH AND CD STRETCHINGS IN CH3CD3

The infrared spectrum of gaseous CH3CD3 has been recorded in the range 3000-15 000 cm-1. Overtone and combination bands up to five quanta of excitation in CH and CD stretchings have been assigned. A total of 71 vibrational states for CH3, involving stretchings and bendings, has been analysed on the basis of a normal mode model. The relations between the normal and local mode parameters associated with CH stretchings were imposed and three Fermi resonance interactions were included. Twelve parameters reproduce the experimental data related to CH3 with an r.m.s. error of 2.16. Less satisfactory results have been obtained by treating 36 vibrational states involving stretchings and bendings of the CD3 group with the same model.