Laser-Enhanced Ionization Spectrometry

Vol. 136. Laser-Enhanced Ionization Spectrometry. Edited by John C. Travis and Gregory C. Turk... 

Photothermal Spectroscopy Methods for Chemical Analysis. By Stephen E. Bialkowski Element Speclatlon in Bioinorganic Chemistry. Edited by Sergio Caroli Laser-Enhanced Ionization Spectrometry. Edited by John C. Travis and Gregory C. Turk Fluorescence Imaging Spectroscopy and Microscopy. Edited by Xue Feng Wang and Brian Herman... 

Laser-enhanced ionization (LEI) is one of a family of laser-induced ionization techniques which have been exploited for analytical spectrometry. The laser-induced ionization schemes which are important for flame spectrometry are illustrated in Fig. 1. 

Laser-enhanced ionization spectrometry should occupy a prominent position in analytical methodology because of the high sensitivity and precision which it provides. Because of the simplicity of the detection scheme, LEI is an easily-implemented and useful complement to other laser-based techniques as well. 

Turk, G. C. et al. Laser-Enhanced Ionization Spectrometry for Trace Metal Analysis, in Proc. Colloque Intemat. CNRS No. 352, Editions de Physique, Aussois, France, June 20-25, 1983... 

Sources for atomic spectrometry include flames, arcs, sparks, low-pressure discharges, lasers as well as dc, high-frequency and microwave plasma discharges at reduced and atmospheric pressure (Fig. 5) [28], They can be characterized as listed in Table 2. Flames are in thermal equilibrium. Their temperatures, however, at the highest are 2800 K. As this is far below the norm temperature of most elemental lines, flames only have limited importance for atomic emission spectrometry, but they are excellent atom reservoirs for atomic absorption and atomic fluorescence spectrometry as well as for laser enhanced ionization work. Arcs and sparks are... 

Fig. 127. Flame laser enhanced ionization spectrometry [670, 671]. (a) Flashlamp/dye laser, (b) high voltage, (c) trigger photodiode, (d) preamplifier, (e) pulse amplifier, (f) active filter, (g) boxcar averager, (h) chart recorder. (Reprinted with permission from Ref. [671]).

Atomic absorption, optical emission and atomic fluorescence as well as plasma mass spectrometry and new approaches such as laser enhanced ionization now represent strong tools for elemental analysis including speciation and are found in many analytical laboratories. Their power of detection, reliability in terms of systematic errors and their costs reflecting the economic aspects should be compared with those of other methods of analysis, when it comes to the development of strategies for solving analytical problems (Table 20). 

Havrilla G. J., Weeks S. J. and Travis J. C. (1982) Continuous wave excitation in laser enhanced ionization spectrometry, Anal Chem 54 2566-2570. 

ESCA electron spectroscopy for chemical analysis (X-ray photoelectron spectroscopy) ESI electrospray ionization ET-AAS (Also denoted GFAAS, EAAS, EA-AAS, ETAAS, ETA-AAS) electrothermal atomization atomic absorption spectrometry ETA-CFS electrothermal atomization -coherent forward scattering (atomic magneto-optic rotation) spectrometry ETAES electrothermal atomization atomic emission spectrometry ETAES electrothermal atomization atomic fluorescence spectrometry ETA-LEI electrothermal atomization -laser enhanced ionization spectrometry... 

In atomic laser spectroscopy, the laser radiation, which is tuned to a strong dipole transition of the atoms under investigation, penetrates the volume of species evaporated from the sample. The presence of analyte atoms can be measmed by means of the specific interaction between atoms and laser photons, such as by absorption techniques (laser atomic absorption spectrometry, LAAS), by fluorescence detection (laser-induced fluorescence spectroscopy, LIFS), or by means of ionization products (electrons or ions) of the selectively excited analyte atoms after an appropriate ionization process (Figures lA and IB). Ionization can be achieved in different ways (1) by interaction with an additional photon of the exciting laser or of a second laser (resonance ionization spectroscopy, RIS, or resonance ionization mass spectrometry, RIMS, respectively, if combined with a mass detection system) (2) by an electric field applied to the atomization volume (field-ionization laser spectroscopy, FILS) or (3) by collisional ionization by surrounding atoms (laser-enhanced ionization spectroscopy, LEIS). 

LEIS laser-enhanced ionization spectroscopy FILS field ionization laser spectroscopy RIS resonance ionization spectroscopy RIMS resonance ionization mass spectrometry... 

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