We discuss the vibrational and rotational state distributions of ground-state O-2 following the photodissociation of O-3 in the Chappuis band. They are obtained from time-dependent wave packet calculations employing ab initio potential energy surfaces for the 1 (1)A " and 2 (1)A " electronic states and the nonadiabatic elements, which couple these states. The satisfying agreement with experimental results underlines that the essential mechanisms of this two-state process are well described.