High resolution quantum cascade laser spectroscopy of the simplest Criegee intermediate, CH 2 OO, between 1273 cm -1 and 1290 cm -1

• Published in: The Journal of chemical physics Vol. 146; no. 24; p. 244302
• Main Authors: Chang, Yuan-Pin, Merer, Anthony J, Chang, Hsun-Hui, Jhang, Li-Ji, Chao, Wen, Lin, Jim Jr-Min
• Format: Journal Article
• Language: English
• Published: United States 28.06.2017

The region 1273-1290 cm of the ν fundamental of the simplest Criegee intermediate, CH OO, has been measured using a quantum cascade laser transient absorption spectrometer, which offers greater sensitivity and spectral resolution (<0.004 cm ) than previous works based on thermal light sources. Gas phase CH OO was generated from the reaction of CH I + O at 298 K and 4 Torr. The analysis of the absorption spectrum has provided precise values for the vibrational frequency and the rotational constants, with fitting errors of a few MHz. The determined ratios of the rotational constants, A'/A″ = 0.9986, B'/B″ = 0.9974, and C'/C″ = 1.0010, and the relative intensities of the a- and b-type transitions, 90:10, are in good agreement with literature values from a theoretical calculation using the MULTIMODE approach, based on a high-level ab initio potential energy surface. The low-K (=K ) lines can be fitted extremely well, but rotational perturbations by other vibrational modes disrupt the structure for K = 4 and K ≥ 6. Not only the spectral resolution but also the detection sensitivity of CH OO IR transitions has been greatly improved in this work, allowing for unambiguous monitoring of CH OO in kinetic studies at low concentrations.