Laser ablation overview

This paper presents an overview of the current research issues and commercialization efforts related to laser ablation for chemical analysis, discusses several fundamental studies of laser ablation using time-resolved shadowgraph and spectroscopic imaging, and describes recent data using nanosecond laser pulsed ablation sampling for ICP-MS and LIBS. Efforts towards commercialization of field based LIBS systems also will be described. 

Inductively coupled plasma mass spectrometry is now such an important technique in archaeology, as elsewhere, that we devote a whole chapter to it. There are now a number of different ICP MS modes of operation (solution analysis, laser ablation, multicollector, high resolution) this chapter provides a general overview. Further description of the instrumentation for ICP MS may be found in Harris (1997) and Montaser (1998). Some general applications of solution ICP MS are discussed by Date and Gray (1989), Platzner (1997), and Kennett et al. (2001). 

Figure 2.9 Overview of sample introduction methods and hyphenated techniques used in ICP-AES. (A) Pneumatic concentric (sometimes called the Meinhard nebuliser) (B) Babington (C) fritted disc (D) Hildebrand nebuliser (E) cross flow (G) standard ultrasonic nebuliser for aqueous and non-aqueous solvents (H) electro-thermal graphite ( ) electro-thermal carbon cup (K) graphite tip filament (L) laser ablation (M) hydride generation (P) flow injection...

The purpose of LA-ICP/MS use is to remove material from the surface and transport it into the ICP for ionization to obtain isotope ratios quickly with little sample preparation. Inter-element isotope ratios are also important in certain radionuclide applications, but are compromised by fractionation issues. Laser ablation provides an overview of which analytes and isotopes are present and approximates the concentration of each. 

The uranium content in soil can be determined directly by some analytical methods that are mainly based on nuclear techniques (variations of neutron activation analysis, gamma spectrometry, x-ray fluorescence, or laser-ablation ICPMS), but the common, popular, and more accurate methods require digestion and dissolution of the entire soil sample or at least rely on leaching the uranium out of the sample matrix. In principle, the methods used for assaying uranium in minerals (see Chapter 2) are also suitable for soil characterization, but uranium is usually present in the latter only as a low-level impurity, usually below 100 pg U g. We shall first overview the procedures deployed for the treatment of soil samples prior to analysis and refer to the analytical devices used for the measuranent of the uranium content and isotopic composition in these studies. 

An issue of Chemical Reviews (volume 103, number 2,2003) covered laser ablation of molecular substrates and included several articles on MALDl. A microscopic view of desorption/ablation was provided by the molecular dynamics work of the Zhigilei and Garrison groups, while Dreisewerd presented an overview of MALDl desorption, and one recently developed cluster model was summarized and further developed by Karas and Kriiger. Secondary mechanisms were examined in detail by Knochenmuss and Zenobi. ... 

Over time, geoscience applications of the basic technique have proliferated, aided by the development of a variety of sample introduction systems, most notably laser ablation. More recently, the use of single- and double-focusing mass spectrometers has enabled workers to resolve interferences not readily resolved on quadrupole-based systems and to determine isotope ratios with high precision. This chapter aims to provide an overview of the geoscience applications of this multifaceted technique. 

This overview on analytical atomic spectrometry touches on the basics of three dominant methods of conducting optical spectroscopy for the purposes of qualitative and quantitative elemental analysis. There are a number of variations in sources, atom cells, dispersive devices, etc. that have not been discussed. As an example, laser-induced breakdown spectroscopy employs a high-intensity laser to ablate samples where the extreme radiant energy also produces a plasma that ultimately produces electronic excitation of the ablated material. Similarly, there are a number of nonoptical approaches that represent variations of some of these schemes that have... 

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