Optical emission spectrographic

Figure 2.2 Schematic drawing of an optical emission spectrograph. Light from the sample is focused onto the input slit of the spectrograph and is then dispersed via a prism (or diffraction grating) and recorded on a photographic plate. (Adapted from Britton and Richards, 1969 Fig. 108, by permission of Thames and Hudson Ltd.)...

Table VI shows the major element composition of the samples as determined by the various laboratories. This table was compiled to emphasize that while there are large discrepancies in the results, most of the laboratories could characterize the samples correctly. Thus, sample 1 is a moderately high tin bronze (Sn ca. 15% ) with about 1% lead and little iron or zinc. Laboratories that fail on the tin value in this characterization are 01 (old), and 04 (old), possibly 05 with a tin value of 20% (although this is an optical emission spectrographic value and falls in the right range), 24 (which doesn t claim any accuracy for its tin result), and 34. Laboratory 01 (old) also has a low lead value as do 08 and 24. Thus, six of 23 laboratories (or about 25% of the results) fail to characterize the samples correctly while the other 17 characterize this sample as a moderately high tin bronze with a little lead.

Table II. Approximate Visual Lower Limits of Determination for the Elements Analyzed by the Optical Emission Spectrographic Technique ...

Figure 4,9. Schematic diagram of an optical emission spectrograph.

Highly sensitive iastmmental techniques, such as x-ray fluorescence, atomic absorption spectrometry, and iaductively coupled plasma optical emission spectrometry, have wide appHcation for the analysis of silver ia a multitude of materials. In order to minimize the effects of various matrices ia which silver may exist, samples are treated with perchloric or nitric acid. Direct-aspiration atomic absorption (25) and iaductively coupled plasma (26) have silver detection limits of 10 and 7 l-lg/L, respectively. The use of a graphic furnace ia an atomic absorption spectrograph lowers the silver detection limit to 0.2 l-ig/L. 

Optical emission spectroscopy includes the observation of flame-, arc-, and spark-induced emission phenomena in the ultraviolet, visible, and near infrared regions of the electromagnetic spectrum [38]. Qualitative and quantitative information can be gained from the intensity of the characteristic emission wavelengths. Analysis of lead in environmental samples (e.g., soils, rocks, and minerals) may be performed reproducibly down to the 5 ppm level. Emission spectroscopy is best used for the multi-elemental analysis of samples, because of the high cost of equipment. Usually, single element analyses are not performed on a emission spectrograph. 

Por IR-Raman experiments, a mid-IR pump pulse from an OPA and a visible Raman probe pulse are used. The Raman probe is generated either by frequency doubling a solid-state laser which pumps the OPA [16], or by a two-colour OPA [39]. Transient anti-Stokes emission is detected with a monocliromator and photomultiplier [39], or a spectrograph and optical multichannel analyser [40]. 

We have observed three subgiants HD 23249 (KO), HD 198149 (KO), HD 222404 (Kl) and three dwarfs HD 10780 (KO), HD 4628 (K2), HD 201091 (K5), on 2002 November 28 and 29, with the high-resolution cross-dispersed echelle spectrograph SOFIN, mounted on the Nordic Optical Telescope (NOT). They are in the solar neighbourhood (< 15 pc), are very bright (V < 6) and have modest projected rotational velocities (v sin i < 4 km s 1) to limit blends between spectral lines. They also do not present any evidence for emission (or a moderate one, as in the case of the three dwarfs) in the core of Ca II H and K lines. 

William Frederick Meggers. Physicist at the U. S. Bureau of Standards since 1914. Chief of die spectroscopy section. Author of many papers on optics, astrophysics, photography, measurement of wave-length standards, and description and analysis of spectra. The instrument in the foreground is a concave grating spectrograph, used for photographing the emission spectrum of rhenium (41). 

To isolate specific emissions of the analyte being analysed (i.e. optical transitions), a high quality optical set-up is required. Dispersive systems using planar, concave or echelle gratings are used in classical spectrophotometers or spectrographs (Figs. ll.lO and 15.6). 

Studies of atmospheric properties using IR spectroscopy techniques have been reported in the literature for nearly 100 years. This paper presents a brief historical review of the development of this area of science and discusses the common features of spectrographic instruments. Two state of the art instruments on opposite ends of the measurement spectrum are described. The first is a fast response iri situ sensor for the measurement of the exchange of CO2 between the atmosphere and the earth s surface. The second is a rocketborne field-widened spectrometer for upper atmosphere composition studies. The thesis is presented that most improvements in current measurement systems are due to painstakingly small performance enhancements of well understood system components. The source, optical and thermal control components that allow these sensors to expand the state of the art are detailed. Examples of their application to remote canopy photosynthesis measurement and upper atmosphere emission studies are presented. 

In-situ luminescence measurements have been used to study the semiconductor/ electrolyte interface for many years (e.g. Petermann et al., 1972). Luminescence may result from optical excitation of electron/hole pairs that subsequently combine with the emission of light (photoluminescence). Alternatively, minority carriers injected from redox species in the electrolyte can recombine with majority carriers and give rise to electroluminescence. The review by Kelly et al. (1999) summarises the main features of photoluminescence (PL) and electroluminescence (EL) at semiconductor electrodes. The experimental arrangements for luminescence measurements are relatively straightforward. Suitable detectors include a silicon photodiode placed close to the sample, a conventional photomultiplier or a cooled charge-coupled silicon detector (CCD). The CCD system is used with a grating spectrograph to obtain luminescence spectra. 

For EL, the devices were driven under constant forward bias (Ca negative with respect to PEDOT PSS / ITO) and their emission was recorded using an Oriel InstaSpec IV spectrograph. The temperature was varied using a continuous-flow He cryostat (Oxford Instruments OptistatCF). For PL, the devices were optically excited through the ITO anode using a 407-nm pulsed diode laser (Pico-Quant LDH400). 

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