Investigation into time evolution of chlorine emission in pulsed CO2 laser induced breakdown spectroscopy (LIBS)

Detection of chlorine (Cl) using LIBS technique is greatly influenced by experimental conditions including the delay time of the detecting device. Time evolution of Cl emission in plasma produced on polyvinyl chloride (PVC) sample using CO₂ laser with variation of delay time has been carried out. The plasma was produced at atmospheric pressure under different environment of helium and air, respectively. It was found that when using the pulse energy of 750 mJ under helium surrounding, strong emission line of Cl at 479.45 nm can be observed until 4 μs of delay time, while when using laser energy 2500 mJ strong Cl emission line can be observed until 7 μs. The higher signal to background ratio was observed at delay time of 1 μs. However, Cl emission line cannot be detected under air environment.