Re-analysis of the high resolution FTIR spectrum of C2H2D2-cis in the region of 1280-1400 cm(-1)

The high-resolution infrared spectrum of C₂H₂D₂-cis ethylene was analyzed in the region of 1280-1400 cm^-1, where the strong ν₁₂ band is located. More than 2000 transitions (about three times more than it was made in the preceding studies) were assigned with the maximum values of the upper quantum numbers J^max.=45 and K_a^max.=19 (J^max.=31 and Kamax.=13 in the preceding studies). For the first time, 22 transitions belonging to the 2ν₁₀ weak band were assigned. For description of the assigned transitions (upper ro-vibrational energy levels), the Hamiltonian model was used which takes into account resonance interactions between the vibrational state (v₁₂=1) and three other closely located states: (v₁₀=2), (v₈=v₁₀=1), and (v₃=1). A set of 43 spectroscopic parameters obtained from a weighted least square fit reproduces the initial experimental data (817 upper energy values and more than 2000 transitions) with the d_rms=2.2×10^-4cm^-1 which is close to experimental uncertainties and considerably better than in prior studies. Ground state rotational and centrifugal distortion parameters were improved on the basis of the IR experimental data of the present study and microwave data from the earlier literature.