Fig. 1. Schematic of LIBS experimental setup

Fig. 2. Schematic of imaging and observation system

Fig. 3. Plasma emission spectrum of Cr element measured in experiment

Fig. 4. Emission spectra of laser-induced plasma at different positions. (a) Cr atomic spectral lines with wavelengths of 425.43, 427.48, and 428.97 nm; (b) Cr ionic spectral line with wavelength of 283.56, 284.32, and 284.98 nm

Fig. 5. Spatial evolution characteristics of emission spectral line intensities. (a) Atomic lines; (b) ionic lines

Fig. 6. Saha-Boltzmann multi-line plots of plasma emission spectral lines of Cr element at different longitudinal positions. (a) -0.8 mm; (b) 0 mm; (c) 0.8 mm; (d) 1.6 mm

Fig. 7. Electron temperatures at different longitudinal positions

Fig. 8. Electron densities at different longitudinal positions