We determined calcium-to-fluorine (Ca/F) signal ratios at the surface and in the depth dimension in approximately 6000-year-old sheep and cattle bones using Ca I 671.8 and F I 685.6 emission lines. Because the bones had been previously analyzed for collagen preservation quality by measurement of C/N ratios at the Oxford Radiocarbon Accelerator Unit, we were able to examine the correlation between our ratios and quality of preservation. In the bones analyzed in this experiment, the Ca I 671.8/F I 685.6 ratio was generally lower and decreased with successive laser pulses into poorly preserved bones while the ratio was generally higher and increased with successive laser pulses into well-preserved bones. After 210 successive pulses, a discriminator value for this ratio (5.70) could be used to distinguish well-preserved and poorly preserved bones regardless of species.
Laser-induced breakdown spectroscopy (LIBS) is used to analyze chemically etched polytetrafluoroethylene (PTFE). The elements O, F, H, and Na are determined qualitatively in the depth dimension. It is shown that O, H, and Na signals are greatest at the surface and decrease as the laser burrows through the etched layer into the bulk. In contrast, the fluorine signal is a minimum at the surface and increases with depth. The average ablation rate for PTFE under the experimental conditions is found to be 1.9 microm per pulse. Using this value, the depth of the etched layer is determined to be 8 microm. A calibration curve produced by analysis of different polymers gives mole fractions of O, F, and H at the surface of the etched PTFE of 0.2, 0.3, and 0.1, respectively.
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