Diagnostics of Ar/N2 mixture plasma with detailed electron-impact argon fine-structure excitation cross sections

Highlights: • A collisional radiative model is developed for electron beam generated ArN₂ mixture plasma at low pressure. • The model uses relativistic distorted wave electron-excitation cross sections of fine-structure transitions from ground and excited states of Ar. • The plasma electron density (n_e) and temperature (T_e) with N₂ concentration are obtained using emission lines of 3p⁵4p (2p) → 3p⁵4s (1 s) transitions. • The 1s_i and 2p_i populations at extracted plasma parameters and are reported. • The contributions to the 2p_i states from the excitations of ground and 1s_i states are reported. A collisional-radiative model is developed for the Ar/N₂ mixture plasma using reliable fully relativistic electron impact excitation cross sections of argon. We consider several fine structure transitions of argon and their corresponding cross sections used in the model have been obtained using fully relativistic distorted wave (RDW) theory. Processes, which account for the coupling of argon with nitrogen molecules, have been further added in the model. The applicability of the model with the RDW cross sections is tested by coupling it to the recent available spectroscopic measurements for a low pressure electron beam generated Ar/N₂ plasma. The plasma parameters viz. electron density (n_e) and electron temperature (T_e) are evaluated by optimizing the model simulated intensities with the eight emission lines (out of 3p⁵4p (2p_i) → 3p⁵4s (1s_i) transitions) observed through the measurements. We find from our study that as the concentration of N₂ increases in the Ar/N₂ mixture from 0 to 10%, our extracted electron density varies from 2.3 × 10¹¹ to 2.8 × 10¹¹ cm⁻³ and the electron temperature decreases from 1.0 to 0.43 eV which are in good agreement with the available probe measurement. Using present collisional radiative model, the individual contributions from the ground and 1s_i states to the radiating states are also evaluated as a function of N₂ concentrations.