| Description |
Double pulse laser induced breakdown spectroscopy in orthogonal configuration was used for the analysis of twelve samples of volcanic glass. Raw material and artifact samples originated from Czech, Slovak, German, Hungarian, Greek, Turkish, and Ukrainian sites. The primary 266 nm laser beam was focused onto a sample area of about 0.1 mm in diameter at the optimised energy of 10 mJ resulting in only very slight sample damage, almost unrecognizable even by a microscope. The secondary 1064 nm laser beam, positioned parallel to the sample surface and focused onto the intersection with the primary beam, induced a spark with enhanced radiation at the optimised energy of 100 mJ. Measurement of emission lines selected on basis of chemical composition, signal intensity, signal-to-background ratio, and minimum interference from the surrounding spectra: Si(I) 288.16 nm, Mg(II) 279.55 nm, 280.27 nm, Mg(I) 285.21 nm, Ca(II) 317.93 nm, Na(I) 589.59 nm, Al(I) 308.22 nm, Fe(II) 259.94 nm, Ti(II) 334.94 nm, Sr(II) 407.77 nm, Ba(II) 455.40 nm, K(I) 769.90 nm, provided experimental data sufficiently sensitive to differentiate the properties of the studied samples. Rare earth elements were not detected even though the double pulse technique is more sensitive than the single pulse variant. Visualisation methods of multidimensional statistical analyses such as radar chart, Chernoff faces, scatterplots, and the Spearman correlation matrix provided successful differentiation of the sample groups and/or particular samples by their origin.
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