High-resolution spectroscopy of C2H3D: Line positions and energy structure of the strongly interacting ν10,ν7,ν8,ν4 and ν6 bands

Abstract

High resolution infrared spectra of C₂H₃D were recorded in the region of 550-1950 cm^-1 with a Bruker IFS125 HR Fourier transform infrared spectrometers and rotational structures of the five lowest strongly interacting ν₁₀, ν₇,ν₈,ν₄ and ν₆ bands were analyzed. The number of about 28000 transitions (4200/6800/5600/5000/6400 for the bands ν₁₀,ν₇,ν₈,ν₄ and ν₆) with J^max = 40 and K_a^max = 20 were assigned to these five bands. The weighted fit of 3990 upper energy values obtained from the experimentally recorded transitions was made with a Hamiltonian which takes into account resonance interactions between all studied bands as well as with the sixth ν₃ band which was considered in this case as a "dark" one. As the result of analysis, a set of 279 fitted parameters was obtained which reproduces the initial 3990 upper "experimental" ro-vibrational energy values with the d_rms=1.7×10^-4 cm^-1; the initial nonsaturated, unblended and not very weak of 28000 assigned transitions are reproduced with the d_rms=2.2×10^-4 cm^-1. Ground state parameters of the C₂H₃D molecule were improved as well.

Keywords: High resolution spectroscopy of ethylene; Resonance interactions in asymmetric top molecules; Spectroscopic parameters.