Temporal evolution of laser plasma temperature

Plasma was produced by laser-induced breakdown in air using the 10.6 μm beam from an pulsed CO2 laser. The plasma spectra were collected by the spectrometer and ICCD. The plasma temperasure was calculated by using the model of local thermodynamic equilibrium. When the laser pulse energy was 35 J, according to the relative intensities of two atom spectral lines NⅡ399.5 nm and NⅡ500.5 nm, the temperature of the plasmas at different time delays was evaluated. It is demonatrated that, the temporal evolution of plasma temperature is ascent-saturation-descent by sampling at the different positions of the plasma, and the temperature at the front edge of the plasma is sooner to become saturated than the temperature near the target.