High-resolution infrared spectrum of CD3CN:: Analysis of the interacting ν3 and ν6 bands and evaluation of the A0 constant

The infrared spectrum in the range 300-1230 cm(-1) including the fundamental bands v(3) and v(6) of CD3CN has been studied. The resolution attained was 0.0025 cm(-1) in the measurement on the Bruker 120 HR Fourier spectrometer in Oulu. About 4000 lines were assigned in the v(6) band. For the weak (v)3 band, which has not been observed earlier directly, we were able to assign 20G lines in three subbands K = 8-10. These lines become detectable due to the strong v(3)/v(6) Coriolis resonance. There is also an l(1, -2) resonance between v(3) and v(6), which made it possible to obtain a value 2.637721(50) cm(-1) for the axial rotational constant A(0), when D-0(K) from force field calculations was applied. Different types of resonances with the overtone 3v(8) and the combinations v(4) + v(8) and v(7) + v(8) were observed. A fit with a standard deviation of 0.0019 cm(-1) was attained by using a model of 10 different resonances (C) 2001 Academic Press.