First high resolution analysis of the ν1+ν2 and ν2+ν3 bands of S18O2

•First high resolution analysis of the ν1+ν2/ν2+ν3 bands of S18O2.•Resonance interactions.•Determination of spectroscopic parameters.

The Fourier-transformed infrared spectra of the ν1+ν2 and ν2+ν3 bands of S18O2 were recorded for the first time in the region 1580-1850 cm−1 and theoretically analyzed. About 940 and 1210 transitions were assigned in the experimental spectra with the maximum values of quantum numbers Jmax./Kamax. equal to 60/20 and 60/21 to the bands ν1+ν2 and ν2+ν3. The weighted fit of experimentally assigned transitions was made with the Hamiltonian model which takes into account Coriolis resonance interaction between the vibrational states (110) and (011) and Fermi interaction between the states (110) and (030). To make the ro-vibrational analysis physically more suitable, the initial values of main spectroscopic parameters have been estimated from the values of corresponding parameters of the S16O2 species on the basis of the results of the isotopic substitution theory. Finally, the set of 26 spectroscopic parameters obtained from the fit reproduces values of 1229 initial “experimental” ro-vibrational energy levels (about 2150 transitions assigned in the experimental spectra) with the drms=1.8×10−4cm−1.