The millimeter-wave rotational spectrum of CF3CCD in the excited vibrational state v10=2

The millimetre-wave rotational spectra of the excited vibrational state v₁₀=2 of the symmetric top molecule, CF₃CCD, have been recorded for J^′′=12 up to J^′′=25. The l=±2 and l=0 series have been assigned and the spectra analysed to give rotational parameters including x_ll=7716.975 MHz. The main interactions between states of different l are the r_t(2,−1)=0.158 MHz and q_t⁺(2,2)=3.308 MHz. Two type of l-resonance are identified, one of which is due to an avoided crossing between the l=0 and l=+2 series. The spectra are qualitatively similar to the corresponding ones of CF₃CCH.