Measuring the electron density in plasmas from the difference of Lorentzian part of the widths of two Balmer series hydrogen lines

•An alternative method to measure the electron density in plasmas from two Balmer series hydrogen lines (Hα and Hβ) is presented.•The method is very convenient for plasmas with electron densities of the order of 1014 cm− 3 and above, at low gas temperatures.•It has been applied to the determination of the electron density of an argon microwave plasma at atmospheric pressure.•Results from it are in good agreement with previous ones obtained using other diagnostic methods.

We present an alternative optical emission spectroscopy method to measure the plasma electron density from the difference of widths of two Balmer series hydrogen lines (Hα and Hβ), especially convenient for non-thermal plasmas since with this method, there is no need to know either the gas temperature or the van der Waals contribution to the Lorentzian part of the line. In this paper it has been assumed that the part of full width at half maximum due to Stark broadening can be determined with the approximation of Lorentzian line shape. The method has been applied to the determination of the electron density in an argon microwave-induced plasma maintained at atmospheric pressure, and comparison with the results obtained using other diagnostic methods has been done.