Study of radiative and kinetic properties of femtosecond laser ablated brass plasma by optical emission spectroscopy

Abstract

Femtosecond laser induced plasma (LIP) in brass was characterized by optical emission spectroscopy (OES). The LIP spectra is dominated by emission from excited neutral species of Cu and Zn. The ionic emission lines are found to decay more rapidly compared to the atomic emission lines. Time resolved OES studies on the expanding plasma plume have provided some insight into probable excitation pathways and the temporal behavior of the excited species.

Further assuming local thermodynamic equilibrium (LTE), the fs-LIP source was characterized for excitation temperature and electron number densities by using the Boltzmann plot method and the width of Stark broadened line profiles respectively. The influence of laser fluence on excitation temperature and electron density was also investigated. The emission intensities exhibit two ablation regimes corresponding to ablation dominated by optical penetration depth at low fluence and by electron thermal diffusion length at higher fluence. Comparative studies on the behavior of copper emission lines from both pure copper and brass samples suggest that femtosecond laser pulses might mitigate the matrix effect in the ablation process.