Fig. 1. Experimental setup of femtosecond LIBS

Fig. 2. Time-integrated spectra of Zn (I) and Cu (I) lines with circular and linear polarizations (laser energy is 1.5mJ). (a) Time-integrated spectrum of Zn (I) line with circular polarization; (b) time-integrated spectrum of Zn (I) line with linear polarization; (c) time-integrated spectrum of Cu (I) line with circular polarization; (d) time-integrated spectrum of Cu (I) line with linear polarization

Fig. 3. Time-resolved spectra of Cu (I) lines with circular and linear polarizations (laser energy is 1.5mJ). (a) Circular polarization; (b) linear polarization

Fig. 4. Evolution of peak intensities of Cu (I) 510.55nm and Zn (I) 472.21nm lines with delay time under circular and linear polarizations (laser energy is 1.5mJ)

Fig. 5. Typical Boltzmann plots. (a) Circular polarization, delay time of 0.4μs; (b) circular polarization, delay time of 0.5μs

Fig. 6. Stark broadening frofile of Cu(I) 510.55 nm spectral line. (a) Circular polarization, delay time of 0.4μs; (b) circular polarization, delay time of 0.5μs

Fig. 7. Evolution of electron temperature and density with delay time under circular and linear polarizations(laser energy is 1.5mJ). (a) Electron temperature; (b) electron density