The density profiles of N2(A3Σu+) and N2(a′Σu-) in the Pink Afterglow of the DC nitrogen flowing discharge

We have studied by optical emission spectroscopy (OES) the afterglow of a nitrogen DC flowing discharge in such experimental conditions that the Pink Afterglow (PA) was present in the post-discharge. The spectra were recorded in the range of 360-435 nm. The emissions of the second positive system of the nitrogen molecules concerning the transitions N-2(C-3 Pi(u), v) -> N-2(B-3 Pi(g), v') with Delta v = -2 and the emissions of the first negative system concerning the transitions N-2(+)(B-2 Sigma(+)(u), v) -> (N-2(+)(X-2 Sigma(+)(g), v') with Delta v = -1 were utilized to furnish the relative density of the N-2(C-3 Pi(u), 0 <= v <= 4) and the N-2(+)(B-2 Sigma(+)(u), 0 <= v <= 6) populations from that we have estimated the total density of the N-2(C-3 Pi(u)) and N-2(+)(B-2 Sigma(+)(u)) electronic states. A kinetic numerical model was constructed for modeling the nitrogen post-discharge. The density profiles of the electronic states N-2(C-3 Pi(u)) and N-2(+)(B-2 Sigma(+)(u)) obtained experimentally were fitted by the calculated density profiles furnished by the model. In this sense, we have calibrated the numerical model that will be employed in the calculation of the coefficients applied in the estimation of the N-2(A(3)Sigma(+)(u)) and N-2(a'Sigma(-)(u)) density profiles. We have developed a method of combined application of the OES and numerical modeling which permits the estimation of the N-2(A(3)Sigma(+)(u)) and N-2(a'Sigma(-)(u)) density profiles from the measured density of the N-2(C-3 Pi(u)) state corrected by the calculated coefficients. The estimated density profiles are compared to the calculated ones generated by the kinetic model. The N-2(A(3)Sigma(+)(u)) densities along the afterglow obtained by our method are compared to those ones measured by intracavity laser absorption spectroscopy (ICLAS) (Sadeghi et al., 2001 [14]). The N-2(a'Sigma(-)(u)) density profile in the PA, based on experimental data, is estimated for the first time here. The N-2(A(3)Sigma(+)(u)) density found in the maximum of the Pink Afterglow is 2.0 x 10(11) cm(-3) and the density of the N-2(a'Sigma(-)(u)) state is 1.3 x 10(11) cm(-3). The discharge operated at 30 mA electric current, 500 Pa gas pressure and 500 sccm flow rate. (C) 2014 Elsevier B. V. All rights reserved.