Optical emission spectroscopy of a discharge in an argon-nitrogen mixture sustained by terahertz radiation from a free-electron laser

This paper describes the results of a study of a discharge in an argon-nitrogen mixture created by a focused beam of radiation at a wavelength of 130 $\mu$m from the Novosibirsk Free Electron Laser (NovoFEL). The results of a study of the population of nitrogen molecules in a fixed electronic-vibrational state under various discharge conditions are presented. Possible mechanisms for the observed population distribution are discussed.