The vibrational energy pattern in acetylene. V. (C2H2)-C-13

A total of 134 vibrational levels with assigned rotational structure have b een gathered in the ground electronic state of (C2H2)-C-13. Most of these m easurements are updated or new compared to the previously published data. A ltogether, they cover the range up to 23 670 cm(-1). 118 out of the 119 lev els observed below 13 000 cm(-1) have been simultaneously fitted using the so-called cluster model, already used to deal with the vibrational energy l evels in other isotopomers of acetylene [El Idrissi , J. Chem. Phys. 110, 2 074 (1999), and references therein]. Twenty-nine vibrational constants have been determined, including the off-diagonal parameters K-3/245, K-1/244, K -1/255, K-11/33, K-14/35, and r(45), with a rms of the fit equal to 0.52 cm (-1). The same three constants of the motion as in (C2H2)-C-12 emerged, N-s =v(1)+v(2)+v(3), N-r=5v(1)+3v(2)+5v(3)+v(4)+v(5) and k=l(4)+l(5). The energ ies of the levels above 13 000 cm(-1) calculated with the obtained paramete rs compare reasonably well with the experimental values. For all levels the predicted rotational constants compare satisfactorily with the experimenta l results. (C) 1999 American Institute of Physics. [S0021-9606(99)00326-8].