Early- and late-time dynamics of laser-produced plasmas by combining emission and absorption spectroscopy

Abstract Optical emission spectroscopy and laser absorption spectroscopy are two highly complementary techniques for diagnosing plasmas, specifically determining important parameters such as temperature and density. In this work, we characterized a laser-produced plasma by combining emission and tunable laser absorption spectroscopy. Plasmas are produced by focusing pulses from a frequency quadrupled Nd:YAG laser onto a glass target containing a minor concentration of aluminum in an ambient atmosphere of ~100 Torr N2. Emission spectroscopy is used to investigate the line behavior of Al and Ca, electron density, and excitation temperature at times ≤ 5 μs, while absorption spectroscopy is used to investigate the line behavior of Al and Ca, species density, and kinetic temperature at times ≥ 5–100 μs. A comparison is made between the excitation temperature measured from emission using the Boltzmann plot method and the kinetic temperature measured from absorption; the implications of this comparison on local thermodynamic equilibrium and line-of-sight averaging are discussed. Combining the two methods of optical emission and laser absorption spectroscopy, a comprehensive characterization of the plasma over the entire lifetime of its evolution is possible, leading to a greater understanding of plasma behavior.