Millimeter-wave spectra of HCCCN

Abstract

The rotational spectra of cyanoacetylene (HCCCN) were investigated between 148 and 474GHz. The assignments were obtained on the basis of a global analysis, which uses both vibrational and rotational data available for this molecule. The 876 new experimental frequencies concern 181 vibrational states (up to about 1750cm−1). The global analysis agreement is perfect for states up to 1300cm−1 and the fit remains good for higher energy states. High order anharmonic interactions associated with the k45577 and k45666 terms of the potential energy, which are not introduced in our model, are responsible for local effects in a few states. The reduced frequencies are plotted for most reported states to illustrate the effects of the numerous interactions. A state-by-state fit is also given, but the classical power series in J(J+1) is not convenient for the heavily perturbed states.