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 a… Show more
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
“…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.…”
Section: Introductionmentioning
confidence: 99%
“…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.…”
“…[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.…”
mentioning
confidence: 99%
“…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.…”
mentioning
confidence: 99%
“…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 ( )…”
Criegee intermediates (CIs) are a class of reactive radicals that are thought to play a key role in atmospheric chemistry through reactions with trace species that can lead to aerosol particle formation. Recent work has suggested that water vapor is likely to be the dominant sink for some CIs, although reactions with trace species that are sufficiently rapid can be locally competitive. Herein, we use broadband transient absorption spectroscopy to measure rate constants for the reactions of the simplest CI, CH2OO, with two inorganic acids, HCl and HNO3, both of which are present in polluted urban atmospheres. Both reactions are fast; at 295 K, the reactions of CH2OO with HCl and HNO3 have rate constants of 4.6×10−11 cm3 s−1 and 5.4×10−10 cm3 s−1, respectively. Complementary quantum‐chemical calculations show that these reactions form substituted hydroperoxides with no energy barrier. The results suggest that reactions of CIs with HNO3 in particular are likely to be competitive with those with water vapor in polluted urban areas under conditions of modest relative humidity.
Criegee intermediates (CIs) are a class of reactive radicals that are thought to play a key role in atmospheric chemistry through reactions with trace species that can lead to aerosol particle formation. Recent work has suggested that water vapor is likely to be the dominant sink for some CIs, although reactions with trace species that are sufficiently rapid can be locally competitive. Herein, we use broadband transient absorption spectroscopy to measure rate constants for the reactions of the simplest CI, CH2OO, with two inorganic acids, HCl and HNO3, both of which are present in polluted urban atmospheres. Both reactions are fast; at 295 K, the reactions of CH2OO with HCl and HNO3 have rate constants of 4.6×10−11 cm3 s−1 and 5.4×10−10 cm3 s−1, respectively. Complementary quantum‐chemical calculations show that these reactions form substituted hydroperoxides with no energy barrier. The results suggest that reactions of CIs with HNO3 in particular are likely to be competitive with those with water vapor in polluted urban areas under conditions of modest relative humidity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.