We report the observation of a rotationally resolved ν 6 band associated with the OO-stretching mode of the simplest Criegee intermediate, CH 2 OO, 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 ν 6 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 ν 6 and ν 8 of CH 2 OO. According to the distinct temporal profiles, lines of a hot band near 899.5 cm -1 were also identified.