The ν3-ν9 band of CD3CD3: A global frequency analysis of data from the three lowest vibrational states

The weak ν3-ν9 difference band of CD3CD3 in the far-infrared region (around 250 cm−1) has been recorded with a Bruker IFS-120 HR Fourier transform spectrometer to extend the observation of the rotational levels to K⩽13 in v3=1 state. This spectrum is analyzed with data from the ν3 and ν9 fundamentals, the ν9+ν4-ν4 hot band and transitions from the ν4 and 3ν4 torsional bands. The combined data set includes more than 3600 frequencies, and was fitted to within experimental accuracy using a 40-parameter model Hamiltonian. No additional resonances were observed between the upper state and the bath states, hence no new intervibrational interactions were required in analyzing the band.