Anomalous broadening and shift of emission lines in filaments

摘要

The temporal evolution of width and shift of N I 746.8 and O I 777.4 nm lines is investigated in filament plasma produced by tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). Nitrogen line shift is determined by joint action of electron impact shift and far-off resonance AC Stark effect. Intensive (I~ 10~(10) W/cm~2) electric field of ASE and post-pulses result in possible LS coupling break for O I 3p ~5P level and generation of Rabi sidebands. The blue-shifted main femtosecond pulse and Rabi sideband cause the stimulated emission of N_2 1~+ system.