Spatio-temporal characterization of N2(A3Σu+) metastables in diffuse nitrogen barrier discharges

The absolute N-2(A(3)Sigma(+)(u), v = 0) metastables density was measured by single photon laser-induced fluorescence spectroscopy in a diffuse nitrogen barrier discharge. The measured absolute metastables density at a gap distance of 1 mm and a pressure of 500 mbar is in the range of 10(13) cm(-3). Its time dependence shows the typical delay of the maximum with respect to the discharge current. The measured axial metastables density profiles reveal that most metastables are produced in front of the anode during the discharge pulse. This is in agreement with the Townsend-like discharge mode of the diffuse nitrogen barrier discharge. Besides the measurements, the metastables behavior in the afterglow of the discharge is modeled to estimate the secondary electron emission by metastables from the previous half cycle on the discharge ignition. The modeling shows that the metastables density is large enough to influence the secondary electron emission and discharge ignition significantly.