The vibrational energy pattern in acetylene (IV): Updated global vibrationconstants for (C2H2)-C-12

All 253 vibrational levels in the ground electronic state of (C2H2)-C-12 wi th assigned rotational structure reported in the literature from absorption , stimulated emission pumping, and dispersed laser induced fluorescence spe ctroscopic investigations are gathered. They cover the range up to 18 915 c m(-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 mo tion, as previously used to deal with the vibrational energy levels up to 1 2 000 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 level s, 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 di scussed and globally attributed to problems of a vibration-rotation nature. A comprehensive listing of calculated vibrational energies for all k suble vels up to 15 000 cm(-1), including predicted B-upsilon values and assignme nts is made available. (C) 1999 American Institute of Physics. [S0021-9606( 99)02404-6].