High-resolution infrared study on DCCI: harmonic force field of monoiodoacetylene

A high-resolution infrared spectrum of DCCI has been measured in the regions of the bands of 2ν₁, ν₁+ν₂, ν₂+ν₃, ν₂+ν₄, ν₂+ν₅, and ν₄+ν₅. Using these bands together with the spectra measured previously, the rovibrational states of 2ν₁, ν₁+ν₂, ν₁+ν₃, ν₁+ν₄, ν₁+ν₅, ν₁+2ν₅, ν₂+ν₃, ν₂+ν₄, ν₂+ν₅, ν₂+2ν₅, ν₃+ν₄, ν₄+ν₅, and ν₄+2ν₅ have been analyzed. Various l-type and Fermi resonances have been taken into account in the analysis. In addition, the weak Coriolis resonance between the levels υ₃=υ₄=1 and υ₄=2 has been considered. Accurate values for the molecular constants and the appropriate resonance parameters have been obtained. The unperturbed normal vibrational frequencies associated to the equilibrium state have been calculated for both isotopic species HCCI and DCCI. Then the harmonic force constants for monoiodoacetylene have been determined.