Laser-driven fluorescence emission in a nitrogen gas jet at 100 MHz repetition rate

We report the fluorescence emission which is driven by femtosecond laser pulses with a repetition rate of 100 MHz and center wavelength 1040 nm in nitrogen gas jet. The experiment performed enhancement cavity coupled high laser. In contrast to previous observation at low jet, where 391-nm radiation was observed but 337-nm missing, three times stronger than our experiment. By examining dependence intensity on flow polarization pump pulse, formation mechanism ${\mathrm{N}}_{2}(C\phantom{\rule{0.16em}{0ex}}^{3}\mathrm{\ensuremath{\Pi}}_{u})$ triplet excited state, i.e., upper state emission, investigated. attribute main excitation process inelastic collision exclude possibility dissociative recombination as dominate pathway. role steady-state plasma that generated under experimental conditions also discussed.