PNNL

Abstract

The electronic structure of the simplest Criegee intermediate (H2COO) is practically that of a closed shell. On the biradical scale (ß) from 0 (pure closed shell) to 1 (pure biradical) it registers a mere ß=0.10, suggesting that a Lewis structure of a H2C=Od+-Od- zwitterion best describes its ground electronic state. However, this picture of a nearly inert closed shell contradicts its rich atmospheric reactivity. It is the mixing of its ground with the first triplet excited state, which is a pure biradical state of the type H2C•-O-O•, that is responsible for the formation of strongly bound products during reactions inducing atmospheric particle growth. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. This research also used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.