Imaging spectroscopy of Ag plasmas produced by infrared nanosecond laser ablation

Abstract

Spatially and temporally resolved optical emission spectroscopy has been used to study plasmas formed by 1064 nm pulsed laser ablation of silver targets in a vacuum. Ag and Ag⁺ species were mapped as a function of both locations from the surface of the target and time from the laser pulse. Plasma parameters such as temperature and electron density were measured from the spatiotemporal analysis. We examined the properties of Ag resonance and non-resonance emission lines and Ag⁺ ions. The results show a faster decay of the continuum emission and Ag⁺ species than in the case of neutral Ag atoms. Higher velocities and a narrower temporal distribution of Ag⁺ are observed in a vacuum when compared to Ag atoms. Electron temperature was assessed from the comparison of the Ag atomic/ionic Saha-local thermodynamic equilibrium spectrum with experimental ones at various delay times from the laser pulse incidence. An initial electron temperature of 2 eV and electron density of 2 × 10¹⁸ cm⁻³ were measured from the spatially integrated spectra.