Abstract : Research has been performed to determine fundamental properties of negative ions; decay mechanisms and products of molecular Rydberg states; and mechanisms affecting H- production in ion source discharges. Experiments were performed on both stable and metastable states of Ca-, Cs-, He 2-, and WO3-; on the dissociative decay of Rydberg states of H3, D3, D2H, H2D, NeH, NeD, NH, CH, and 02; on the product states of dissociative recombination of Ar2 and Kr2; and on the vibrational distribution of O2+ resulting from the reaction O+ + C02 yields O2+ + CO. Negative Ions, Molecular Rydberg States, Predissociation.