Figure 5

Measured side-spectra lines: (a) with the laser filament only and when the aluminum target is located at the (b) beginning, (c) middle, and (d) end of the filament. The slit width and exposure time for collection using a grating spectrometer with a grating with 300 grooves/mm are: (a) 100 µm and 500 ms, (b) 100 µm and 10 ms, (c) 50 µm and 8.24 ms, and (d) 100 µm and 1000 ms, respectively. The nitrogen lines were identified using the results reported in ref.³⁹.