Tunneling splittings in the rotational spectrum of

Abstract

The splitting of some rotational lines due to a predicted hydrogen atom migration in protonated acetylene, [Formula: see text], was not observed in the first pure rotational spectroscopy experiment in the vibrational ground state. An improvement of the spectral resolution of the spectrometer has allowed the observation of some of these small splittings. They have been interpreted within the semi-rigid bender model. Numerical results are presented for different values of the barrier height. Reasonable agreement between observed and calculated splittings is obtained with a barrier of about 1600 cm−1, which is 15% higher than the most recent ab initio value.