High-resolution synchrotron FTIR spectroscopic analysis of the Coriolis interaction between the v10=1 and v8=1 states of ethylene-cis-1,2-d2

The synchrotron Fourier transform infrared (FTIR) spectrum of the b-type io band of ethylene-cis-1,2-d(2) (cis-C2H2D2) was recorded eta resolution of 0.00096 cm(-1) in the 550-750 cm(-1) region. The measured FWHM of the lines was about 0.002 cm(-1). The vio band, centred at 662.871885(27) cm(-1) was found to be perturbed through a b-type Coriolis resonance with the infrared inactive 3 at 759.9582(20) cm(-1). In this work, 1989 infrared transitions of vio were assigned for the first time. These perturbed and unperturbed infrared transitions were fitted with an rms deviation of 0.00033 cm(-1) using the Watson's A-reduced Hamiltonian in the 1(r) representation with three Coriolis terms to derive the rovibrational constants for v(10) =1 and v(8) =1 states. Ground state rovibrational constants up to two sextic terms were also derived from a fit of a total of 2532 ground state combination differences with arms deviation of 0.00030 cm(-1) from the infrared transitions of the present analysis and those determined previously. The ground state constants compared favourably to the equilibrium state constants from harmonic cc-pVTZ basis set at CCSD(T), MP2 and B3LYP levels. The rotational constants of io and v from this work agree well with those from enharmonic calculations.