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- Axner, Ove, 1957-, et al.
(författare)
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Laser spectrometric techniques in analytical atomic spectrometry
- 2012
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Ingår i: Encyclopedia of analytical chemistry. - Chichester, UK : John Wiley & Sons, Ltd. - 9780470027318
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Bokkapitel (refereegranskat)abstract
- The main purpose of this article is to describe the theory, instrumentation, and analytical performance of laser analytical atomic spectrometry, focusing on absorption, fluorescence, and ionization techniques. The structure of the article is such that it first provides an outline of the theory of light-matter interactions that prevail for each type of technique as well as of the most common modulation techniques, primarily, wavelength modulation (WM). This is followed by a section that covers the most important types of instrumentation used. The article finally provides a detailed discussion on the specific instrumentation, mode of operation, use, performance, and applications (both analytical and diagnostic) of each technique. In terms of laser atomic absorption, the focus of the discussion is on the use of approaches to enhance the detection capability by either reducing the amount of noise (as is done by the wavelength modulation absorption spectrometry (WMAS) technique) or by providing an extended interaction length (giving rise to cavity-enhanced absorption spectrometry (CEAS) techniques in general, and cavity ring-down spectrometry (CRDS) in particular). Laser atomic fluorescence techniques (often referred to as laser-excited atomic fluorescence spectrometry (LEAFS)) as well as laser ionization techniques (termed either laser-enhanced ionization (LEI) or resonance ionization spectrometry (RIS)) are also covered in some detail. It is shown that several of these techniques are capable of detecting a variety of elements in liquid samples down to low picogram per milliliter (pg mL−1) or parts-per-trillion (ppt) concentrations and in low femtogram amounts. Also other properties of the techniques, e.g. selectivity and linear dynamic range (LDR), are in general superior to those of conventional (nonlaser-based techniques).
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| 2. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrumentation for Doppler-broadened detection in the 10-12 cm-1 Hz-1/2 region
- 2012
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:6, s. 1305-1315
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Tidskriftsartikel (refereegranskat)abstract
- A fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry (FL-NICE-OHMS) system for white-noise-limited Doppler-broadened detection down to 5.6 x 10(-12) cm(-1) Hz(-1/2) is demonstrated. The system is based on a previous FL-NICE-OHMS instrumentation in which the locking of the laser frequency to a cavity mode has been improved by the use of an acousto-optic modulator (AOM) and provision of a more stable environment by the employment of a noise-isolating enclosed double-layer table, a temperature regulation of the laboratory, and an ultra-high-vacuum (UHV) gas system. White-noise behavior up to 10 s provides the instrument with a minimum detectable on-resonance absorbance per unit length of 1.8 x 10(-12) cm(-1) and a relative single-pass absorption (Delta I/I) of 7.2 x 10(-11). The system was applied to detection of acetylene on a transition at 1531.588 nm, yielding a detection sensitivity of C2H2 in atmospheric pressure gas of 4 ppt (measured over 10 s). (C) 2012 Optical Society of America
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| 3. |
- Silander, Isak, 1980-, et al.
(författare)
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Frequency modulation background signals from fiber-based electro optic modulators are caused by crosstalk
- 2012
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:5, s. 916-923
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Tidskriftsartikel (refereegranskat)abstract
- Frequency modulated spectroscopy (FMS) performed by the use of fiber-coupled electro optic modulators (FC-EOMs) is often plagued by background signals that bring in noise and, by their temperature dependence, cause severe drifts. These signals cannot be zeroed out by the conventional technique of using a carefully adjusted polarizer that can be applied to free space electro optic modulators (EOMs). This can limit the use of FC-EOMs in high performance detection techniques. Here we provide an explanation to these background signals that is based upon crosstalk between various polarization directions of light in the fixed mounted polarization-maintaining fibers and the electro optic crystal. The description provides a basis for the previously demonstrated technique that utilizes an EOM regulated simultaneously by temperature and DC voltage to eliminate background signals from systems encompassing FC-EOMs. (C) 2012 Optical Society of America
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