Peroxyacetyl radical: Electronic excitation energies, fundamental vibrational frequencies, and symmetry breaking in the first excited state Andreas V. Copan, Avery E. Wiens, Ewa M. Nowara, Henry F. Schaefer III, and Jay Agarwal Citation: The Journal of Chemical Physics 142, 054303 (2015); doi: 10.1063/1.4906490 View online: http://dx.doi.org/10.1063/1.4906490 View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/142/5?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Torsion-wagging tunneling and vibrational states in hydrazine determined from its ab initio potential energy surface J. Chem. Phys. 136, 174301 (2012); 10.1063/1.4705267 The electronic spectrum of the fluoroborane free radical. I. Theoretical calculation of the vibronic energy levels of the ground and first excited electronic states J. Chem. Phys. 130, 164309 (2009); 10.1063/1.3122008 Observation of a new phosphorus-containing reactive intermediate: Electronic spectroscopy and excited-state dynamics of the HPBr free radical J. Chem. Phys. 123, 144304 (2005); 10.1063/1.2055227 The disilaketenyl radical (HSiSiO) in its ground and first excited electronic states J. Chem. Phys. 111, 227 (1999); 10.1063/1.479286 The vibrational spectrum of H 2 O 2 +⋅ radical cation: An illustration of symmetry breaking J. Chem. Phys. 106, 4877 (1997); 10.1063/1.473537

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THE JOURNAL OF CHEMICAL PHYSICS 142, 054303 (2015)

Peroxyacetyl radical: Electronic excitation energies, fundamental vibrational frequencies, and symmetry breaking in the first excited state Andreas V. Copan, Avery E. Wiens,a) Ewa M. Nowara,b) Henry F. Schaefer III, and Jay Agarwalc) Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602, USA

(Received 6 December 2014; accepted 10 January 2015; published online 3 February 2015) Peroxyacetyl radical [CH3C(O)O2] is among the most abundant peroxy radicals in the atmosphere and is involved in OH-radical recycling along with peroxyacetyl nitrate formation. Herein, the ˜ and first (A) ˜ excited state surfaces of cis and trans peroxyacetyl radical are characterized ground (X) using high-level ab initio methods. Geometries, anharmonic vibrational frequencies, and adiabatic excitation energies extrapolated to the complete basis-set limit are reported from computations with coupled-cluster theory. Excitation of the trans conformer is found to induce a symmetrybreaking conformational change due to second-order Jahn-Teller interactions with higher-lying excited states. Additional benchmark computations are provided to aid future theoretical work on peroxy radicals. C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4906490]

I. INTRODUCTION

Peroxy radicals (RO2) play an important role in the oxidation of organic compounds at low temperatures (