Vibronic Coupling Effects in the Photoelectron Spectrum of Ozone: A Coupled-Cluster Approach

Area of Science:

• Computational Quantum Chemistry
• Theoretical Spectroscopy
• Molecular Electronic Structure

Background:

• Equation-of-motion coupled-cluster (EOM-CC) theory is crucial for predicting and analyzing electronic spectra.
• Accurate simulation of electronic spectra requires high-level computational methods.
• The ozone cation presents a coupled pair of electronic states (X̃²A₁ and òB₂) requiring precise theoretical treatment.

Purpose of the Study:

• To apply the equation-of-motion coupled-cluster method for ionized states (EOM-IP-CC) to the ozone cation.
• To accurately calculate the electronic and vibronic spectra of the ozone cation.
• To refine the understanding of the energy gap between the X̃²A₁ and òB₂ electronic states.

Main Methods:

• Utilized the equation-of-motion coupled-cluster method for ionized states (EOM-IP-CC) with high-level excitations up to quadruple (EOM-IP-CCSDTQ).
• Employed a robust method for calculating vibronic spectra based on the EOM-IP-CC derived Hamiltonian.
• Compared simulated spectra with experimental photoelectron spectroscopy data for ozone.

Main Results:

• Simulated vibronic spectra show good agreement with the experimental photoelectron spectrum of ozone.
• Calculations indicate the adiabatic energy gap between the X̃²A₁ and òB₂ states is smaller than previously estimated.
• Precise band positions suggest an adiabatic gap (T₀₀) of 1,368 ± 65 cm⁻¹.

Conclusions:

• The EOM-IP-CC method, including high-level excitations, provides accurate electronic and vibronic spectra for the ozone cation.
• The refined adiabatic gap value offers a more precise understanding of the ozone cation's electronic structure.
• The study facilitates accurate assignment of experimental spectral features and improves theoretical models of ozone.