Optical diagnostics of the hollow needle to plate electrical discharge in air at atmospheric pressure

Abstract

Vibrational and rotational excitation of the N2(C 3 Πu) state in a DC hollow needle to plate electrical discharge at atmospheric pressure was studied by means of multichannel emission spectrometry. Vibrational distributions and rotational temperatures of the N2(C 3 Πu) electronic state were obtained for a negative polarity of the needle as a function of mean energy density dissipated in the discharge reactor. Vibrational excitation of the N2(C 3 Πu) apparently decreases with increasing energy density and the shape of vibrational distributions reflects predominant processes responsible for the N2(C 3 Πu) state population, i.e. electron impact excitation of N2(X 1 Σ + g , v) ground state and energy pooling mechanism by N2(A 3 Σ + u ) metastables. Rotational temperatures evolve in the range 1000 ÷ 1800 K and show linear increase with energy density dissipated in the discharge reactor.