A study of non-linear calibration graphs for brass with femtosecond laser-induced breakdown spectroscopy

The ablation of brass samples with 170 fs laser pulses was studied by time resolved emission spectroscopy. The intensities of Cu as well as of Zn line s were found to be non-linearly dependent on their concentrations in the sa mples. This behaviour is explained by changes in the mass ablation rate. Th us, linear dependencies were obtained when the Zn line intensities were nor malized to the line intensities of Cu. A simple theoretical model based on compositional differences is presented. The differences in ablation are acc ounted for using the standard two-temperature diffusion model for short las er pulse ablation and the steady current resistivity as a fundamental param eter describing the compositional changes in a set of brass samples. In pri nciple, it is possible to construct linear calibration curves from the meas ured Zn and Cu line intensities without internal standardization if the mod el and energy dependent ablation measurements are taken into account. Induc tively coupled plasma mass spectrometry measurements are used to demonstrat e this. (C) 2001 Elsevier Science BN. All rights reserved.