Thermodynamic and spectroscopic properties of Nd:YAG–CO2 Double-Pulse Laser-Induced Iron Plasmas

Double-Pulse Laser-Induced Breakdown Spectroscopy of iron using both Nd:YAG and TEA–CO2 lasers has been investigated to better understand mechanisms of signal enhancement. The signal dependence on the delay between the two laser pulses shows an enhanced signal when the CO2 laser pulse interacts with the sample before the Nd:YAG pulse. Signal kinetics and a simple model of sample heating by the CO2 pulse show that the enhancement during the first 700 ns is due primarily to sample heating. Images of the sample surface after ablation as well as time-integrated pictures of the plasma suggest that particles are ejected from the surface during the first microseconds after the arrival of the CO2 pulse and provide fuel for the subsequent plasma created by the Nd:YAG laser.