Langmuir probe and spectroscopic studies of RF generated helium-nitrogen mixture plasmaM. A. Naveed, N. U. Rehman, S. Zeb, S. Hussain and M. ZakaullahEur. Phys. J. D, 47 3 (2008) 395-402DOI: https://doi.org/10.1140/epjd/e2008-00055-9