The vibrational energy pattern in acetylene. V. $C213H2$ Available to Purchase

A total of 134 vibrational levels with assigned rotational structure have been gathered in the ground electronic state of $C213H2.$ Most of these measurements are updated or new compared to the previously published data. Altogether, they cover the range up to $23 670 cm−1.$ 118 out of the 119 levels observed below $13 000 cm−1$ have been simultaneously fitted using the so-called cluster model, already used to deal with the vibrational energy levels in other isotopomers of acetylene [El Idrissi et al., J. Chem. Phys. 110, 2074 (1999), and references therein]. Twenty-nine vibrational constants have been determined, including the off-diagonal parameters $K3/245,$ $K1/244,$ $K1/255,$ $K11/33,$ $K14/35,$ and $r45,$ with a rms of the fit equal to $0.52 cm−1.$ The same three constants of the motion as in $C212H2$ emerged, $Ns=v1+v2+v3,$ $Nr=5v1+3v2+5v3+v4+v5$ and $k=l4+l5.$ The energies of the levels above $13 000 cm−1$ calculated with the obtained parameters compare reasonably well with the experimental values. For all levels the predicted rotational constants compare satisfactorily with the experimental results.