Structural, vibrational, and rovibrational analysis of tetrafluoroethylene

High resolution FTIR spectra of C-13 enriched tetrafluoroethylene (C2F4) were measured at 150 K at the Australian Synchrotron. Rovibrational transitions were assigned in the a-type symmetric and b-type antisymmetric CF2 stretches of (CCF4)-C-12-C-13 and (C2F4)-C-13 near 1170 cm(-1) and 1300 cm(-1), respectively. Ground vibrational state spectroscopic constants for both molecules were determined in addition to the upper state constants for nu(11) and nu(9) of (C2F4)-C-13 and nu(11), nu(2)+nu(6), and nu(5) of (CCF4)-C-12-C-13. The ground state constants, along with those determined for the (C2F4)-C-12 isotopologue from previously published data, were used to determine a semi-experimental r(e) structure r(CC) = 132.36 +/- 0.37 pm, r(CF) = 131.11 +/- 0.23 pm, alpha(FCC) = 123.3 +/- 0.3 degrees in excellent agreement with ab initio structures. Lower resolution FTIR spectra were measured between 100 and 5000 cm(-1) at room temperature and band centres obtained for all modes of the three isotopologues; although only 5 out of 12 modes in (C2F4)-C-12 and (C2F4)-C-13 are infrared (IR) active, the others were inferred from combination and hot-band positions. A number of modes are observed to be infrared active only in the (CCF4)-C-12-C-13 isotopologue due to its lower symmetry. Most notably, decoupling of the antisymmetric CF2 motions in the two halves of (CCF4)-C-12-C-13 results in 2 strongly IR active modes that involve motion at one carbon or the other. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4768417]