Vibronic Coupling\nEffects in the Photoelectron Spectrum\nof Ozone: A Coupled-Cluster Approach

One of the most important areas of application for equation-of-motion\ncoupled-cluster (EOM-CC) theory is the prediction, simulation, and\nanalysis of various types of electronic spectra. In this work, the\nEOM-CC method for ionized states, known as EOM-IP-CC, is applied to\nthe closely lying and coupled pair of states of the ozone cation<i>X̃</i><sup>2</sup><i>A</i><sub>1</sub> and <i>Ã</i><sup>2</sup><i>B</i><sub>2</sub>using\nhighly accurate treatments including up to the full single, double,\ntriple, and quadruple excitations (EOM-IP-CCSDTQ). Combined with a\nvenerable and powerful method for calculating vibronic spectra from\nthe Hamiltonian produced by EOM-IP-CC calculations, the simulations\nyield a spectrum that is in good agreement with the photoelectron\nspectrum of ozone. Importantly, the calculations suggest that the\nadiabatic gap separating these two electronic states is somewhat smaller\nthan currently thought; an assignment of the simulated spectrum together\nwith more precise band positions of the experimental measurements\nsuggests <i>T</i><sub>00</sub> = 1,368 ± 65 cm<sup>–1</sup>.