Laser ablation: Fundamental principles for analytical applications
- Lawrence Berkeley Lab., CA (United States); and others
This paper will discuss fundamental issues influencing the coupling of laser energy to solid surfaces for accurate and efficient chemical analysis. Results from several monitoring techniques are correlated to demonstrate the changes in laser sampling mechanisms as a function of incident power density, the primary parameter influencing the interaction. Inductive Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) is an excellent system for studying laser ablation. The ICP-AES signal intensity is proportional to the power of laser power density (P{sub n}), with two very different power dependencies. At P < 3x108 W/cm2, the slope n is about 3.5 and at P > 3x108 W/cm2 the slope n is about 1.3. These results suggest significant changes in the energy coupling to the material surface as a function of power density. The reduced power dependence, i.e., mass ablation rate, at the higher power densities may be indicative of plasma shielding. Results from ICP-AES measurement are correlated with those from acoustics, laser induced plasma emission intensity show the same two slope behaviors as the ICP-AES data. There also is strong correlation between ICP and laser induced plasma emission intensities over the power density region. All the monitoring techniques show a turning point at about 3x108 W/cm2, in which the mass ablation rate decreases. The correlations of data from these various techniques are discussed in terms of understanding the laser ablation processes for chemical analysis applications.
- OSTI ID:
- 191646
- Report Number(s):
- CONF-941098--
- Country of Publication:
- United States
- Language:
- English
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