Emission spectroscopy of a carbon plasma formed by laser ablation of graphite. II. Ablation by a CO2 laser and also simultaneously by XeCl and CO2 lasers

The method of time-resolved emission spectroscopy was used to investigate the radiation emitted by a carbon plasma plume formed as a result of vacuum ablation of graphite by pulsed CO₂ laser radiation. The spectrum of the radiation changed drastically in the course of emission from the plasma. The spectrum revealed successive appearance of various luminescence components contributed by C⁺ ions, C₂ radicals, and microparticles. This spectrum differed considerably from that observed for a plasma formed by ablation with an XeCl laser, mainly because of the difference between the laser radiation wavelengths. Under certain conditions it was found that additional heating with CO₂ laser radiation of a plasma formed by ablation of graphite with XeCl laser radiation altered greatly the emission spectrum. The changes indicated a higher degree of particle atomisation and a higher proportion of ions in such a plasma, compared with the plasma produced by one laser.