- Accepted Paper
Ultrafast electron-impact-excited N superfluorescence in femtosecond filaments
Phys. Rev. A - Accepted 6 October, 2026
DOI: https://doi.org/10.1103/x1t4-s4sw
Phys. Rev. A - Accepted 6 October, 2026
DOI: https://doi.org/10.1103/x1t4-s4sw
We demonstrate that the 337-nm emission from neutral nitrogen molecules, pumped via incoherent electron-impact excitation in circularly polarized femtosecond filaments, is oscillatory superfluorescence (SF) rather than amplified spontaneous emission (ASE). Time-resolved measurements reveal that both the pulse duration and the emission delay scale as with nitrogen pressure, providing a definitive signature of gain-swept SF. These dynamics are quantitatively reproduced by bidirectional Maxwell-Bloch simulations that incorporate impulsive electron-impact excitation and fine-structure quantum beats. Our results demonstrate that macroscopic quantum coherence emerges following ultrafast electron-impact pumping and persists in atmospheric-pressure plasmas despite rapid collisional dephasing. These results establish femtosecond filament as a robust platform for studying collective molecular phenomena and provide a framework for generating remote, coherent UV sources in the atmosphere.
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