Communication: Determination of the molecular structure of the simplest Criegee intermediate CH2OO

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

“…The ground vibrational state of CH 2 OO has been extremely well characterized by the microwave work of Nakajima and Endo, 34,35 McCarthy et al, 33 and Daly et al…”

“…The effect of isotope substitution was also discussed in a follow-up paper. 31 In the microwave region, both McCarthy et al 33 and Nakajima et al 35 determined precise rotational constants of CH 2 OO and several isotopologues from pure rotational transitions in the ground vibrational state. From these results, structural parameters such as the CO and OO bond lengths could be derived, again indicating more zwitterionic than biradical character.…”

“…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.…”

Perspective: Spectroscopy and kinetics of small gaseous Criegee intermediates

“…A slight variation was employed by Nakajima and Endo, who initially produced CH 2 OO in a supersonic jet with a pulsed electric discharge of a gaseous mixture of CH 2 Br 2 and O 2 diluted in Ar. 22 These authors subsequently employed discharge of CH 2 I 2 and O 2 diluted in Ne to produce vibrationally excited CH 2 OO. …”

“…14 Even though other isomers of CH 2 OO such as dioxirane, methylene bis(oxy), and formic acid (HCOOH) all have m/z (mass to charge ratio) = 46 u, these authors identified the detected species as CH 2 OO because its ionization energy ∼10 eV conforms to theoretical predictions, 9.98 eV, and is smaller than ionization energies of other isomers. After the discovery of this source of CH 2 OO, many researchers utilized this scheme to produce CH 2 OO and reported ultraviolet (UV) depletion, 18 UV absorption, 19,20 infrared (IR) absorption, 21 microwave, 22,23 and submillimeter-wave 24 spectra. Spectra of slightly larger Criegee intermediates such as acetaldehyde oxide (CH 3 CHOO), 15,[25][26][27][28][29][30][31][32] acetone oxide [(CH 3 ) 2 COO], 16,33 and propionaldehyde oxide (C 2 H 5 CHOO) 10 are also reported.…”