The infrared spectrum of (12)C2D2: the stretching-bending band system up to 5500 cm(-1).

The infrared spectrum of the perdeuterated acetylene, (12)C2D2, has been recorded from 900 cm(-1) to 5500 cm(-1) by Fourier transform spectroscopy at a resolution ranging between 0.004 and 0.009 cm(-1). Ninety-two bands involving the ν1, ν2, and ν3 stretching modes, also associated with the ν4 and ν5 bending vibrations and 9 bands involving pure bending transitions have been observed and analysed. In total, 8345 transitions for the stretching-bending, and 862 for the pure bending modes have been assigned in the investigated spectral region. All the transitions relative to each stretching mode, i.e. the fundamental, its first overtone, and associated hot and combination bands involving bending states up to v4 + v5 = 2, were fitted simultaneously. The Hamiltonian adopted for the analysis is that appropriate to a linear molecule and includes vibration and rotation l-type interactions. The Darling-Dennison interaction between v4 = 2 and v5 = 2 levels associated with the various stretching states was also considered. The standard deviation for each global fit is smaller than 0.0006 cm(-1), of the same order of magnitude of the measurement precision.