Femtosecond Laser-Induced Nitrogen Fluorescence Emission At Different Air Pressures

In this paper, we experimentally investigate femtosecond laser-induced nitrogen fluorescence emission at different air pressures (0.1 Pa-100 kPa). The variation of nitrogen molecule (N-2) and molecular nitrogen ion (N-2(+)) characteristic fluorescence spectral lines' intensity as a function of air pressure is observed. When the air pressure is between 10 Pa and 100 kPa, the intensity of fluorescence signals from N-2(+) and N-2 shows opposite variation as a function of air pressure. We deduce that dissociative recombination is the main pathway for the production of the C-3 Pi(u) state of N-2. This research helps elucidate the physical emission mechanism of femtosecond laser-induced nitrogen fluorescence emission. Published under an exclusive license by AIP Publishing.