On the use of the intensity ratio of He lines for electric field measurements in atmospheric pressure dielectric barrier discharge

In this paper a new method is proposed and tested for electric field measurements in the cathode region of a low-temperature atmospheric pressure discharge in helium. The method uses intensity ratio of two helium singlet lines: He I 2¹P–3¹D at 667.8 nm and He I 2¹P–3¹S at 728.1 nm. The correlation between the line intensity and the electric field was firstly obtained via Stark polarization spectroscopy of He I 2¹P–4¹D 492.19 nm line and its forbidden counterpart in a dielectric barrier discharge (DBD) in helium. Collisional–radiative model for the involved atomic levels is utilized to confirm and obtain the functional dependence of the line ratio on the local electric filed strength. Finally, the new method was used for measurement and investigation of space–time evolution of electric field in the atmospheric pressure DBD. (paper)