Temporal evolution of the electron temperature and density in a 1064 nm Nd:YAG laser produced copper plasma

Abstract

In recent years, the study of pulsed laser interaction with matter at laser intensities sufficient to transform matter into plasma has attracted a lot of attention. Aside from understanding the basic processes involved in the interaction, the interest is also driven by its scientific and technological applications such as pulsed laser deposition and spectrochemical or mass analysis of samples. Though laser produced plasma is easy to generate, the fundamental physical and chemical processes in its formation and evolution are not well understood. There is a need for quantitative data to develop a reliable model. Considerable effort is being devoted towards developing diagnostic tools to accurately and completely measure the relevant parameters of the laser produced plasma.
In this study, we investigate the transient plasma generated by the interaction of a pulsed 1064 nm Nd:YAG laser with a copper target through time resolved optical emission spectroscopy. The temporal behavior of the electron temperature and density is computed from the time resolved emission spectra under the assumption of local thermodynamic equilibrium (LTE). The temperature is estimated from the integrated intensities of copper emission lines. The Stark broadening of nitrogen lines is used to deduce the electron density. Finally, the validity of the LTE assumption is examined.