Two harmonics of the Nd:YAG laser at 266 nm and 532 nm were used as the irradiation source for the analysis of several glass standards and soda-lime glass samples of interest to forensic scientists. Both lasers were kept at a constant energy of 20 mJ and focused using a 150 mm focal length lens. A series of experiments were also conducted to determine the importance of wavelength on lens-to-sample distance (LTSD) at each wavelength. It was determined that the optimal LTSD was found at ~ 1-2 mm focused into the surface for both wavelengths yet the crater depth resulting from the irradiation at 266 nm was significantly deeper (112 µm) than that from the 532 nm laser (41 µm). In addition, the analytical performance of LIBS on five NIST glasses and six automobile glasses at both wavelengths is reported. Good correlation for the quantitative analysis results for the trace and minor elements Sr, Ba, and Al are reported, along with the calibration curves, in most cases R2 > 0.95, using absolute intensities at various emission lines. Although 266 nm resulted in more mass removal, the 532 nm produced greater emission intensities. A slightly higher plasma density was determined for irradiation by 532 nm, using the Stark broadening technique compared to the 266 nm irradiation. (publisher abstract modified)
Wavelength Dependence on the Elemental Analysis of Glass by Laser Induced Breakdown Spectroscopy
NCJ Number
255276
Journal
Spectrochimica Acta Part B: Atomic Spectroscopy Volume: 63 Issue: 10 Dated: October 2008 Pages: 1016-1023
Date Published
October 2008
Length
8 pages
Annotation
This article reports on a research project that presents Laser Induced Breakdown Spectroscopy (LIBS) as a tool for the elemental analysis of glass in forensic applications.
Abstract