High-resolution vibration–rotational spectra and rotational perturbation of the OO-stretching (ν6) band of CH2OO between 879.5 and 932.0 cm−1

Abstract

We report the observation of a rotationally resolved ν₆ band associated with the OO-stretching mode of the simplest Criegee intermediate, CH₂OO, in the range of 879.5–932.0 cm⁻¹ (11.37–10.73 μm) at an optical resolution of 0.0015 cm⁻¹. The spectra were recorded with a tunable cw external-cavity quantum-cascade laser (EC-QCL) system coupled with a Herriott multipass absorption cell. Over one thousand lines were assigned to determine the rovibrational parameters of the ν₆ band. Rotational parameters A′, B′, and C′ and higher-order parameters Δ_J, Δ_JK, Δ_K, δ_J, and δ_K were determined precisely. Rotational perturbations for K_a′ = 3, K_a′ = 6, and K_a′ ≥ 11 on high-J levels were observed. In particular, for K_a′ = 6, frequency shifts as a function of J′ showed an avoided crossing; the shifts were analyzed in terms of a Coriolis interaction between modes ν₆ and ν₈ of CH₂OO. According to the distinct temporal profiles, lines of a hot band near 899.5 cm⁻¹ were also identified.