We present the results of an ab initio quantum-chemical investigation of the structure of the anion O-4(-) and potential energy surfaces for several electronic states. In addition to ground-state vibrational frequencies, which are in good agreement with other calculations and with matrix isolation experiments, we have investigated both photodissociation of O-4(-) into various states of O-2 and O-2(-) and dissociative photodetachment leading to a free electron and various states of two O-2 molecules. Our surfaces lead to predictions for both photodissociation and photodetachment processes that are in excellent agreement with experiment. (C) 2001 American Institute of Physics.