This work reports on the results of investigations conducted with three layered polypropylene (PP) membranes which were exposed to a N2 flowing microwave (100 W) post discharge, at several flow rates (0.03–1 Slm) and at gas pressure from 0.3 to 40 Torr. The N atoms transmission through the membrane was measured from the intensity variation of the N2, 580 nm afterglow which is related to N atom density, before and after the membranes. The results obtained showed that N-atoms penetrate and cross the membranes with a transmission factor (TN) varying from 20 to 70% during the exposure time (15 min), depending on flow rate and gas pressure. A maximum value TN = 0.7 (±0.05) is found for sufficient low flow rate (less than 0.1 Slm), that is for low flow gas velocity (about 2 9 102 cm s-1).

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