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Atmospheric and Oceanic Optics

2016 year, number 2

Superradiance on ions of molecular nitrogen in filaments

N.G. Ivanov1, V.F. Losev1,2, V.E. Prokop’ev1,3, K.A. Sitnik1
1High Current Electronics Institute of the Siberian Branch of the RAS, 634055, Tomsk, 2/3, Academichesky ave. HCEI SB RAS
2National Research Tomsk Polytechnic University, 30, Lenin Avenue, Tomsk, 634050, Russia
3National Research Tomsk State University, 36, Lenin Avenue, Tomsk, 634050,Russia
Keywords: филамент, инверсия населенностей, фемтосекундный лазерный импульс, многофотонная ионизация, молекула, ионы, filament, population inversion, femtosecond laser pulse, multiphoton ionization, molecule, ions

Abstract

The experimental results of the study of population inversion in the resonant electronic transition B3П g -A3å u+ of nitrogen ions by optical pump of air and pure nitrogen by a femtosecond laser pulse at a wavelength of 950 nm are presented. It is shown that the inversion results from selective settling of N2+ (B2å u+,n¢=0) excited state during multiphoton excitation of the autoionization state of the nitrogen molecule with energy of 18.7 eV. Seed photons for superradiance at transitions of molecular nitrogen ions are photons of the axial supercontinuum occurring in a filament at the corresponding wavelengths. The mode of the superradiance at the wavelength  = 358.4 nm, referred to the transition of the CN molecules, was implemented.