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Analysis of the active medium parameters of molecular nitrogen ions in ambient air.

In this Letter, we report the direct streak camera measurements of the duration of a lasing pulse from molecular nitrogen ions under various focusing conditions of 10 mJ, 950 nm femtosecond pump pulse in atmospheric pressure air. The parameters of the active medium are analyzed, and a mechanism for formation of picosecond lasing pulse duration at femtosecond seed pulse duration is proposed.