PNNL

Abstract

Kinetics of ion and atom emission features were compared for nanosecond laser-produced plasmas generated from several metal targets (i.e. Al, Ti, Zr, Nb, Ta) and an alloy containing all of these as principal alloying elements. The plasmas were produced by focusing 6 ns, 1064 nm pulses from an Nd:YAG laser on the target of interest in vacuum. A Faraday cup was used for collecting ion temporal features while spatially and temporally resolved emission spectroscopy was used for measuring the optical time of flight of various atomic transitions. Our results highlight that most probable ion and atom velocities decay with increasing atomic mass. Trends for ions from the alloy target represent a weighted average where all ions contribute. For both ions and atoms, velocities decrease with increasing heat of vaporization and melting temperature, consistent with the understanding that thermal mechanisms are dominant in nanosecond laser ablation. Kinetic energies for ions and atoms from pure metal targets have some variability with amu, although kinetic energies for atoms from the alloy target are more similar.