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 2 1 P–3 1 D at 667.8 nm and He I 2 1 P–3 1 S at 728.1 nm. The correlation between the line intensity and the electric field was firstly obtained via Stark polarization spectroscopy of He I 2 1 P–4 1 D 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.