Wavelength Dependence on the Forensic Analysis of Glass by Nanosecond 266 nm and 1064 nm Laser Induced Breakdown Spectroscopy

• NCJ Number: 255277
• Journal: Applied Optics Volume: 49 Issue: 13 Dated: 2010 Pages: C49-C57
• Author(s): Erica M. Cahoon; Jose R. Almirall
• Date Published: 2010
• Length: 9 pages
• Grant Number(s): 2005-IJ-CX-K069
• Agencies: NIJ-Sponsored

Annotation

This article reports on a project that demonstrated how laser induced breakdown spectroscopy (LIBS) can be used for the chemical characterization of glass to provide evidence of an association between a fragment found at a crime scene to a source of glass of known origin.

Abstract

Two laser irradiances, 266 nm and 1064 nm, were used to conduct qualitative and quantitative analysis of glass standards. Single-pulse and double-pulse configurations and lens-to-sample-distance settings were optimized to yield the best laser-glass coupling. Laser energy and acquisition timing delays were also optimized to result in the highest signal-to-noise ratio corresponding to the highest precision and accuracy. The crater morphology was examined, and the mass removed was calculated for both the 266 nm and 1064 nm irradiations. The analytical figures of merit suggest that the 266 nm and 1064 nm wavelengths are capable of good performance for the forensic chemical characterization of glass. The results presented suggest that the 266 nm laser produces a better laser-glass matrix coupling, resulting in a better stoichiometric representation of the glass sample. The 266 nm irradiance is therefore recommended for the forensic analysis and comparison of glass samples. (publisher abstract modified)