The bending vibrations in 12C2H2:: global vibration-rotation analysis

A total of 3155 vibration-rotation line positions providing accurate information on all known vibration-rotation states up to 3000 cm(-1) in (C2H2)-C-12 were gathered from the literature. An additional 966 lines were assigned on new spectra. The full data set was simultaneously fitted using an appropriate Hamiltonian, with 85 refined parameters. A dimensionless standard deviation equal to 0.86, accounting for 92% of the lines, was achieved. The vibrational transition dipole moment of the v(5) = 1 <- v(4) = 1 band observed in the far-infrared was estimated to be vertical bar mu(5 <- 4)vertical bar = 0.55 D with 20% accuracy, from absolute intensity measurements for a few Q-branch lines.