Early stage optical emission in nanosecond laser ablation
This paper describes the results of an experimental and theoretical investigation of the physical origin of the visible continuum emission usually observed in the early stages of nanosecond laser ablation of solid materials. It has been suggested, but not confirmed that the continuum is due to radiative recombination and bremsstrahlung emission. Time and space-resolved emission spectroscopy with an absolutely calibrated spectrometer was used to study the spectral emission in laser ablation of zinc in vacuum at 4.1 J cm−2 using a 8 ns, 1064 nm laser pulse. By modelling the spectral emission with a spectral synthesis code, it has been shown that the continuum emission is primarily due to bound-bound transitions between strongly Stark broadened energy levels. Similarly, it can be concluded that the optical absorption is primarily due to bound-bound transitions.