Ab initio study of the electronic spectrum of the PO2 radical

Ab initio electronic structure calculations are reported for 18 electronic states of the PO2 radical, Geometric parameters for the X (2)A(1) ground state are calculated at the MRD-CI level with a triple-zeta basis set Plus two polarization d functions, as well as Rydberg functions. The vertical excitation energies, oscillator strengths and radiative lifetimes for these states are determined at the ground stale equilibrium conformation. The equilibrium geometries and adiabatic excitation energies for the three lowest-lying electronic excited states 1 B-2(2), 1 (2)A(2) and 1 B-2(1) ((2) Pi(u)), force constants and vibrational frequencies for the X (2)A(1) ground stair and these three excited states are also calculated, and are found to be in good agreement with experimental data.