The vibrational energy pattern in acetylene (IV): Updated global vibration constants for C212H2

Abstract

All 253 vibrational levels in the ground electronic state of C212H2 with assigned rotational structure reported in the literature from absorption, stimulated emission pumping, and dispersed laser induced fluorescence spectroscopic investigations are gathered. They cover the range up to 18 915 cm−1. Some 219 of these energies are simultaneously fitted using the same so-called Cluster model based on the emergence of three constants of the motion, as previously used to deal with the vibrational energy levels up to 12 000 cm−1 [Abbouti Temsamani and Herman, J. Chem. Phys. 103, 5931 (1995)]. Thirty-nine vibrational constants are produced. The rms value of the fit is 0.81 cm−1. Principal rotational constants are predicted for all levels, which satisfactorily compare with the experimental results. Problems are demonstrated to concern a fraction of the 34 remaining levels only. Thus, the adequacy of the model is fully confirmed. The remaining problems are discussed and globally attributed to problems of a vibration–rotation nature. A comprehensive listing of calculated vibrational energies for all k sublevels up to 15 000 cm−1, including predicted Bv values and assignments is made available.