Lowest vibrational states of acrylonitrile from microwave and synchrotron radiation spectra.

The high resolution Fourier-transform spectrum of acrylonitrile covering the 40–700 cm −1 spectral region was recorded at the AILES infrared beamline of the SOLEIL synchrotron. The spectrum allowed assignment of vibration–rotation transitions in four different fundamental bands, five hot bands, one overtone band, as well as of some pure rotational transitions. The new infrared data and previous measurements made with microwave techniques have been combined into a single global fit encompassing over 31 000 measured transitions. Precise vibrational term values have been determined for the eight lowest excited vibrational states, including ν 11 = 228.299930(4), ν 15 = 332.678207(4), ν 10 = 560.716701(5), and ν 14 = 681.793862 ( 13 ) cm −1 . The new values are compared with those obtained previously entirely on the basis of rotational perturbations. Several anharmonicity coefficients are determined and compared with ab initio anharmonic force field calculations. The assignment of the ν 10 mode is also clarified. [ABSTRACT FROM AUTHOR]