Time evolution of the infrared laser ablation plasma plume of SiO

The spatio-temporal evolution of the silicon monoxide SiO plasma produced by a high-power CO₂ pulsed laser has been investigated using optical emission spectroscopy (OES) and imaging methods. The formed plasma was found to be strongly ionized, yielding Si⁺, O⁺, Si²⁺, O²⁺ and Si³⁺ species, rich in neutral silicon and oxygen atoms, and very weak molecular bands of SiO time-integrated and time-resolved two-dimensional OES plasma profiles were recorded as a function of emitted wavelength and distance from the target. The temporal behavior of specific emission lines of Si, Si⁺, O⁺, Si²⁺ and O²⁺ was characterized. The results show a faster decay of O²⁺ and Si²⁺ than that of O⁺, Si⁺ and Si. The Stark broadening of isolated single-ionized silicon emission lines was employed for deducing the electron density during the plasma expansion. The relative intensities of two Si²⁺ lines were used to calculate the time evolution of the plasma temperature.