Terahertz spectroscopy of isotopic acrylonitrile

► Rotational spectra of isotopic acrylonitrile studied up to 1.2 THz. ► Perturbations between g.s. and the v11 = 1 state fitted for four isotopic species. ► Six new doubly substituted isotopic species of acrylonitrile assigned. ► Semi-experimental equilibrium geometry determined.