AbstractThe work presents the spectral investigations on an a.c. plasma display, in order of a better understanding of the physical phenomena taking place in such a device. The spectral characteristics of the panel filled with a Penning mixture Ne + 0.1% Ar are presented and the influence of the nitrogen addition on these characteristics was evidentiated. The presence of the trace of nitrogen in the device may be used in order to evidentiated. The presence of the trace of nitrogen in the device may be used in order to evidentiate small leaks or imperfections in pumping and outgasing processing of the display.