Temperature Measurement of Laser-Induced Plasmas from the Intensity Ratio of Two Lines Emitted from Different Elements with the Same Ionization Degree

A new laser induced plasma temperature measuring method with two lines emitted from different elements with the same ionization degree is proposed, assuming local thermodynamic equilibrium condition of the plasma. The influence of measurement error on deduced temperature accuracy was simulated in theory. A solution containing Cu, K, and Cr elements was used as the sample. Plasma was generated at the surface of the solution, and time-resolved spectra were recorded. Two atomic lines, Cu I 324 nm and K I 766 nm, were used to determine the plasma temperature with the proposed method. Four atomic lines and two ionic lines of Cr were selected to deduce plasma temperature with the Saha–Boltzmann plot method for comparison. The temperatures deduced from the two different methods showed similar behavior as a function of time. The results suggested that this method can be useful in cases where only very few lines from a single element are available in the spectrum and Boltzmann or Saha–Boltzmann plots cannot be built.