Intense, directional UV emission from molecular nitrogen ions in an adaptively controlled femtosecond filament

Abstract

Using phase-shaped millijoule 1030-nm femtosecond pulses generating a filament in a cell filled with N2, we obtain intense forward UV emission between vibrational manifolds of B2Σ and X2Σ states of N2+ for optimal pulse sequences. The effect is tentatively ascribed to wave-mixing between intense NIR pulses and weak supercontinuum components, resonant to the UV transitions, whereby a non-instantaneous nonlinear susceptibility is linked to rotational coherence in ions.