Refined potential-energy surfaces for the X2A" and ? 2A electronic states of the HO2 molecule

In a previous paper (G. Osmann et al. J. Mol. Spectrosc. 197, 262 (1999)) we calculated ab initio the potential-energy surfaces of the ground X2A" and excited ?2Aʹ electronic states of the HO2 molecule; these two states correlate with a 2P state at linearity and participate in a Renner effect interaction. In that paper, we also calculated the electricand magnetic-dipole moment and transition-moment surfaces, and the spin-orbit coupling constant; we then simulated the ? ® Xemission band system including both electric-dipole and magnetic-dipole transitions. We now calculate more points on the surfaces to cover a wider range of bending geometries, and then refine the surfaces by fitting to rovibronic term values for both electronic states simultaneously. In the fitting we include levels having J values up to 9/2 and term values up to about 8000 cm-1. In our calculation of the energy levels we allow for the Renner effect and spin-orbit coupling by using our variational computer program RENNER. A good fitting to the data is obtained and as a result we obtain an accurate representation of these two potential surfaces over an energy range of more than 1 eV. We tabulate the vibronic energies up to 1 eV for both HO2 and DO2. We can explain the origin of a perturbation observed in the F1 spin component levels of the ?(0, 0, 0) vibronic state for J values around 51/2; this is caused by a spin-orbit interaction satisfying D N = ± 1 with the F2 spin component levels of the (1,1,2) vibronic state. Using the new rovibronic energies and wave functions, with our ab initio electric dipole moment and transition moment surfaces, we calculate Stark coefficients and compare them with experiment for some ground vibronic state levels.