Study of the population inversion mechanisms and superradiance on ion transitions of molecular nitrogen in the filament

Abstract

The experimental results of the inversion population mechanisms study in the resonant electronic transition B 3 Π g –A 3 Σ u + of nitrogen ions by optically pumped of air and pure nitrogen by femtosecond laser pulse at a wavelength of 950 nm are presented. It is shown that the inversion results from selective settling of N 2 + (B 2 Σ u + , v' =0) excited state by multiphoton excitation of the autoionization states of the nitrogen molecule with energy of 18.7 eV. Seed photon for superradiance at transitions of molecular nitrogen ions are photons the axial supercontinuum occurring in the filament on the respective wavelengths. The mode of the superradiance at a wavelength λ = 358.4 nm referred to the transition of the CN molecules was realized.