Optical emission of plasmas in ultraviolet and infrared laser ablation of graphite by time-resolved spectroscopy

The optical emission spectra of the plasma produced by infrared and ultraviolet laser ablation of graphite in a vacuum were observed. The fundamental output of an Nd: YAG laser was used as the infrared laser. The fourth harmonic output of an Nd: YAG laser and a KrF excimer laser were used as the ultraviolet lasers. The emission intensity of the ionic carbon as well as C-2 and C-3 from the plasma produced by the infrared laser were stronger than that produced by the UV lasers at the same fluences. The C-2 and C-3 emission intensities decreased rapidly with increasing the distance from the target. The emission intensity of atomic carbon at 247.8 nm from the plasma produced by the KrF excimer laser was much stronger than that produced by the other lasers at the same laser fluence, due to the wavelength of the KrF laser being so close to that of atomic carbon's emission line as to raise its electrical state.