We simulate the vibronic states of the ozone cation using the model Hamiltonian of Köppel, Domcke, and Cederbaum-the KDC Hamiltonian . This is a multi-state and multi-mode Hamiltonian defined in the basis of diabatic states. For the ozone cation, the basis comprises two quasi-diabatic states (related to the 2 A 1 and 2 B 2 states at the minimum of neutral ozone), coupled by one mode (asymmetric stretch, mode number 3). The model also includes two symmetric modes (modes number 1 and 2). The matrix elements of the vibronic Hamiltonian are expanded around the equilibrium geometry of neutral ozone using the respective dimensionless normal coordinates, Q i , and the corresponding harmonic frequencies, ω i . The overall form of the vibronic Hamiltonian is thus: