a b s t r a c t A bi-directional nanosecond pulsed power supply is employed to generate diffuse dielectric barrier discharge in N 2 using needle-plate electrode configuration at atmospheric pressure. Both discharge images and optical emission spectra of diffuse bi-directional nanosecond high-voltage pulsed dielectric barrier discharge are successfully recorded under severe electromagnetic interference. The diffuse performance of the discharge at different electrode gap distances is observed. The effects of pulse peak voltage, pulse repetition rate, electrode gap distance, He addition, and O 2 addition on the optical emission spectra are investigated. The main physicochemical processes involved are discussed. Ó 2012 Elsevier B.V. All rights reserved.