The rotational spectrum of acrylonitrile up to 1.67Â THz

The rotational spectrum of acrylonitrile was studied up to 1.67 THz by recording and analysing several extended spectral segments spanning a total of over 540 GHz. The spectra were obtained with cascaded harmonic multiplication techniques, and the ground state data set was extended to over 3000 lines, J = 129, and includes transitions up to Ka=30. At high-J and Ka several manifestations of a perturbation between the ground state and the lowest excited vibrational state, v11=1, were observed. The perturbed frequencies were successfully fitted with a coupled fit of the two states resulting in E11=228.29991(2)cm-1. The results reported for the parent species of acrylonitrile should allow confident prediction of the major features over the whole envelope of the measurable rotational spectrum. New measurements and spectroscopic constants for the ground states of the three single 13C isotopic species and for the 15N species are also reported.