Measurement of Stark width of some Ar I transitions and the investigation of LTE in an atmospheric DC argon plasma jet

The Stark width of seven Ar I transitions are reported. Axial line shapes from an atmospheric DC argon plasma jet were Abel inverted to obtain radial line shapes. The electron density was determined by Stark width measurements of the hydrogen Hβ transition. In the electron density region of 1.0 to 6.0 x 1022 m-3, the experimental values of Stark width obtained from the observed line shapes agree within 30% with the values predicted by Griem's theory of Stark broadening, except in the cse of the 7504 A transition where the agreement is only 45%. The authors' experimental accuracy is 10% and hence most of the theoretical half widths are not in agreement with the experimental results reported. They also observed the regularities and similarities of the half widths for the 4s-4p and 4p-6s transition arrays. Their measurements show that LTE does not exist below an electron density of 6.0 x 1022 m-3 in the plasma jet