Formation of O2- ions in K(nd)-O2 collisions at intermediate n

Rate constants for the formation of O2- ions in collisions between K(nd) Rydberg atoms and O2 have been measured for values of n in the range 8--12. The measured rate constants are small and decrease from --5 x 10/sup -12/ cm3 sec/sup -1/ at n = 8 to --1 x 10/sup -12/ cm3 sec/sup -1/ at n = 12. The data are consistent with a reaction model in which Rydberg electron attachment leads to the formation of short-lived excited O2- ions, some of which are subsequently stabilized by an interaction with the core ion