title: The Origin of the Reactivity of the Criegee Intermediate: Implications for Atmospheric Particle Growth.
abstract: The electronic structure of the simplest Criegee intermediate, H2COO, is practically that of a closed shell. On the biradical scale (β), where 0 corresponds to the pure closed shell and 1 to a pure biradical, its β value is only 0.10, suggesting that its ground electronic state is best described as a H2C=O(δ+)-O(δ-) zwitterion. However, this picture of a nearly inert closed shell contradicts its rich reactivity in the atmosphere. It is shown that the mixing of its ground state with the first triplet excited state, which is a pure biradical state of the type H2C˙-O-O˙, is responsible for the formation of strongly bound products during reactions inducing atmospheric particle growth.
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, WA, 99352, USA.
authors.forename: Evangelos
authors.identifier: http://orcid.org/0000-0003-3471-7133
authors.initials: E
authors.lastname: Miliordos
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, WA, 99352, USA. sotiris.xantheas@pnnl.gov.
authors.forename: Sotiris S
authors.initials: SS
authors.lastname: Xantheas
keywords: Criegee intermediates; atmospheric chemistry; biradicals; computational chemistry; electronic structure