High resolution absolute absorption cross sections of the B̃¹A′–X̃¹A′ transition of the CH₂OO biradical

Abstract

Carbonyl oxides, or Criegee intermediates, are formed from the gas phase ozonolysis of alkenes and play a pivotal role in night-time and urban area atmospheric chemistry. Significant discrepancies exist among measurements of the strong B ̃(1)A'-X ̃(1)A' electronic transition of the simplest Criegee intermediate, CH2OO in the visible/near-UV. We report room temperature spectra of the B ̃(1)A'-X ̃(1)A' electronic absorption band of CH2OO acquired at higher resolution using both single-pass broadband absorption and cavity ring-down spectroscopy. The new absorption spectra confirm the vibrational structure on the red edge of the band that is absent from ionization depletion measurements. The absolute absorption cross sections over the 362-470 nm range are in good agreement with those reported by Ting et al. Broadband absorption spectra recorded over the temperature range of 276-357 K were identical within their mutual uncertainties, confirming that the vibrational structure is not due to hot bands.

High resolution quantum cascade laser spectroscopy of the simplest Criegee intermediate, CH2OO, between 1273 cm−1 and 1290 cm−1

“…The UV spectra of CH 2 OO under bulk conditions were later reported by three groups: Sheps 27 using cavity-enhanced absorption spectroscopy, Ting et al 25 using single-pass absorption spectroscopy, and Foreman et al 28 using single-pass absorption and cavity ring-down spectroscopy. Utilizing the fact that SO 2 reacts quickly with CH 2 OO, Ting et al 25 obtained a reliable UV absorption spectrum of CH 2 OO, which is consistent with later reports.…”

“…6,7,12,13 CH 2 OO is the simplest CI, and is therefore the prototypical CI for elucidating important issues of reactivity and structure. Spectroscopic characterizations of CH 2 OO have been carried out extensively in the vacuum ultraviolet (VUV), 2,24 ultraviolet (UV), [25][26][27][28] infrared, 29-31 microwave [32][33][34][35] and terahertz 32 regions. Taatjes et al 2,24 reported the first direct identification of CH 2 OO by employing VUV photoionization mass spectroscopy, which can detect selectively ionized CH 2 OO instead of its more stable isomers.…”

Reactions between Criegee Intermediates and the Inorganic Acids HCl and HNO3: Kinetics and Atmospheric Implications

“…[31] Pulsed laser photolysis of CH2I2 at 355 nm generated CH2I radicals, which reacted rapidly with O2 to produce CH2OO in high yield. [32][33][34][35][36] Transient absorption spectroscopy using broadband pulsed LEDs was used to measure the time-dependent concentration of CH2OO in the absence and presence of a controlled concentration of acid.…”

“…The LED output spanned the wavelength range 365-388 nm, capturing several characteristic vibronic bands of the CH2OO B̃-5 X̃ transition. [31,37,38] Selectivity is important because secondary chemistry results in formation of IO, [35,39] which absorbs in the same spectral window. Typical transient spectra obtained at several time delays in the absence of acid are shown in Figure 1.…”

“…Typical transient spectra obtained at several time delays in the absence of acid are shown in Figure 1. The absorbance transients are fit to linear combinations of reference spectra, [31,40] ( )⁄ = CH 2 OO CH 2 OO ( )…”