Electrostatic Probe Studies of the Nitrogen Pink Afterglow

Studies of the short-duration nitrogen pink afterglow (PA) are reported for different electrostatic probe types (spherical and cylindrical) and materials (Pt and Au). Various collision-dominated probe theories were applied to determine the electron density Ne and temperature Te. Experimental radial distribution curves are presented for the parameters kTe, Ie / Ii (electron to ion current ratio), and Ne at various points in the PA. An apparent increase in the ion current caused by emission of electrons from the probe surface was found to correlate with the light emission intensity of the first negative bands of N2+. kTe was found to be about 1 eV upstream of the PA in the dark space, reaching a maximum of nearly 4.5 eV before decreasing again to 1 eV downstream. The maxima in the axial profiles through the PA of Te, the light emission intensity and the ion current coincide, while Ne (in the range 1–5 × 109 cm−3) shows its maximum a few milliseconds later. The effect of impurities on the PA was examined. The role played by electrons in the process of PA formation is discussed.