Filament; AC Stark effect; Rabi sideband; Line broadening; Amplified spontaneous emission;INDUCED BREAKDOWN SPECTROSCOPY; SPECTRAL-LINES; RADIATION; SYSTEM

he temporal evolution of the width and shift of NI746.8 and OI777.4 nm lines is investigated in a filament plasma produced by a tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). The nitrogen line shift and width are determined by the joint action of electron impact shift and the far-off resonance AC Stark effect. The intensive (I = 1.2.10(10) W/cm(2)) electric field of ASE (amplified spontaneous emission) and post-pulses result in a possible LS coupling break for the OI3p P-5 level and the generation of Rabi sidebands. The blueshifted main femtosecond pulse and Rabi sideband cause the stimulated emission of the N-2 1(+) system. The maximal widths of emission lines are approximately 6.7 times larger than the calculated Stark widths. (C) 2017 Elsevier B.V. All rights reserved.