The role of high Rydberg states in enhanced O- formation in a pulsed O-2 discharge

Formation of O- ions in a pulsed discharge of O-2 was investigated in a Lan gmuir-probe-assisted photodetachment experiment. A large enhancement of neg ative ion formation was observed in the afterglow. Experimental results are consistent with O- formation via electron attachment to high Rydberg state s of O-2 that survive into the afterglow. Such excited states can be produc ed by high-energy electron impact during the discharge. The lifetime of hig h-Rydberg molecules is estimated to be longer than 10 microseconds. The eff icient production of O- ion by electron attachment to high-Rydberg O-2 mole cules was further confirmed in a laser excitation experiment. The O- ions a nd O atoms produced via enhanced dissociative electron attachment to excite d states of O-2 may be important for the chemical processes that occur in p ulsed plasma remediation of contaminated air.