Criegee intermediates (CIs) play a vital role in the atmosphere – known most prominently for enhancing the oxidizing capacity of the troposphere. Knowledge of their electronic absorption spectra is of vital importance for two reasons: (1) to aid experimentalists in detecting CIs and (2) in deciding if their removal is affected by solar photolysis. In this poster we report how a simple and efficient method based on the nuclear ensemble method may be effectively used to compute the electronic absorption spectra of Criegee intermediates without the need for extensive computation of preparing the initial configurations of the geometry. We use this method to benchmark several excited state electronic structure methods and how effective they are in reproducing the electronic absorption spectra of two well-known CIs: CH2OO and CH3CHOO. The success of the methodology is crucial for its application to CIs of increasing molecular complexity, that do not have experimentally measured electronic absorption spectra – allowing a guide for experimentalists. Application of the methodology to more complex CIs will also reveal if solar photolysis becomes a competitive removal process when compared to unimolecular decay or bimolecular chemistry. We employ a simple Wigner distribution to generate a plethora of starting geometries for CH2OO. Despite the molecule’s simplicity, the resulting absorption spectrum is in excellent agreement with the experimentally found absorption spectrum and future studies will include using these benchmarks to study Criegee intermediates of increasing molecular complexity.

Simplified and efficient simulation of the absorption spectra of criegee intermediates: Theory and benchmarking of CH2OO and CH3CHOO

ACS Spring Meeting 2021

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