The results of an optical emission study of neon and oxygen species which exist in Ne/O2rf diode sputtering glow discharges are presented. Comparing emission intensities in pure Ne and Ne/O2mixtures at constant total gas pressure, it was found that the addition of O2to the sputtering gas quenches Ne i emission and increases emission from O i and O+2species to a greater extent than that which would be expected from the relative changes in neon and oxygen concentrations, respectively. Although this effect could be caused by a change in the electron density and electron energy distribution function, the correlation between Ne i, O i, and O+2emission suggests that metastable neon atoms may interact directly with ground state diatomic oxygen molecules in two competing ways: (1) by Penning ionization which produces O+2, and (2) by a quasiresonant transfer of excitation which leads to the production of O. The results are compared to those previously obtained for Ar/O2discharges using identical sputtering conditions, where the dominant interaction between the rare gas and O2leads entirely to the production of monatomic oxygen.