Study of highly excited ro-vibrational states of S¹⁸O₂ from “hot” transitions: The bands ν₁+ν₂+ν₃−ν₂, 2ν₁+ν₂−ν₂, and 2ν₂+ν₃−ν₂

Transitions belonging to the three “hot” bands of the S¹⁸O₂ molecule, ν₁+ν₂+ν₃−ν₂ (621 transitions with the values of quantum numbers J^max=49 and K_a ^max=14), 2ν₁+ν₂−ν₂ (332 transitions with J^max=42 and K_a ^max=12) and 2ν₂+ν₃−ν₂ (15 transitions with J^max=14 and K_a=8 and 9), were assigned in the spectral 2100–2700 cm⁻¹ region. This enabled for the first time to get high accurate values of 388, 185 and 13 ro-vibrational energies for the highly excited vibrational states (111), (210) and (021), respectively. A weighted fit analysis using the obtained ro-vibrational energies allowed us to generate a set of 20 fitted parameters which reproduce the initial 586 energy values (about 970 assigned experimental transitions) with the d_rms deviations of 1.9×10⁻⁴cm⁻¹, 2.8×10⁻⁴ cm⁻¹ and 2.5×10⁻⁴ cm⁻¹ for the states (111), (210) and (021).