Estimation of minima in 1A1 states of the ozone molecule

Calculations have been made at the minima of the X¹A₁ ground state of the ozone molecule. The equilibrium geometries have been obtained by means of CID calculations. The criterion adopted for the choice of configurations gives realistic results. CIPSI calculations at the two minima lead to an estimated gap of 0.92 eV between them. Our results agree with the analysis of previous theoretical works on the relative stability of open and cyclic zone structures, showing that the D_3h minimum is stable relative to the ground state dissociation limit.