Detection, simultaneous

A linear array of photodiodes providing the ability to detect simultaneously radiation at several wavelengths. 

Unlike the array collector, with a microchannel plate all ions of only one m/z value are detected simultaneously, and instrument resolution does not depend on the number of elements in the micro-channel array or on the separation of one element from another. For a microchannel plate, resolution of m/z values in an ion beam depends on their being separated in time by the analyzer so that their times of arrival at the plate differ. 

ICP-OES is one of the most successful multielement analysis techniques for materials characterization. While precision and interference effects are generally best when solutions are analyzed, a number of techniques allow the direct analysis of solids. The strengths of ICP-OES include speed, relatively small interference effects, low detection limits, and applicability to a wide variety of materials. Improvements are expected in sample-introduction techniques, spectrometers that detect simultaneously the entire ultraviolet—visible spectrum with high resolution, and in the development of intelligent instruments to further improve analysis reliability. ICPMS vigorously competes with ICP-OES, particularly when low detection limits are required. 

The advantage of the imaging mode is fast data acquisition. Because all pixels are projected and detected simultaneously the measurement time for one distribution is extremely low. 

Katritzky and co-workers studied the mechanism of this reaction in detail. His work involved a NMR study of 16 reactions of methyl-, phenyl-, 1,2-dimethyl-, and l-methyl-2-phenylhydrazine with /3-keto esters. In many cases starting materials, intermediates, and products were detected simultaneously. Most reactions proceed by nucleophilic addition of the less hindered hydrazine nitrogen atom to the keto carbon of the keto ester. For example, the pathway given in Scheme 3 for the reaction of methyl 3-oxobutanoate 9 with methyl- or phenyUiydrazine 2 (R = Me or Ph) was found to be dominant. The initially formed addition product 10 dehydrates to hydrazone 11, which then isomerizes to hydrazone 12. Intermediate 12 then cyclizes to pyrazol-3-one 13, which tautomerizes to the kinetically more stable pyrazol-3-otie 14 [87JCS(P2)969]. 

Lowering the temperature has a similar effect on the deuterium spectra as does increased loadings. In Figure 3, spectra for benzene-d6/(Na)X at 0.7 molecules/supercage over the temperature range 298 to 133 K are shown. It is observed that both benzene species are detected simultaneously between 228 and 188 K. Below this temperature the oriented benzene species becomes the predominant form. A similar situation occurs for polycrystalline benzene-dg in which two quadrupole patterns, one static and the other motionally narrowed due to C rotation, are observed to coexist at temperatures between 110 and 130 K (7). This behavior has been attributed to sample imperfections (8) which give rise to a narrow distribution in correlation times for reorientation about the hexad axis. For benzene in (Na)X and (Cs,Na)X such imperfections may result from the ion/benzene interaction, and a nonuniform distribution of benzene molecules and ions within the zeolite. These factors may also be responsible for producing the individual species. However, from the NMR spectra it is not possible to... 

Adjustable Workbench (PAW) instrument assembly. The SH shown in Figs. 3.15 and 3.16 contains the electromechanical transducer (mounted in the center), the main and reference Co/Rh sources, multilayered radiation shields, detectors and their preamplifiers and main (linear) amplifiers, and a contact plate and sensor. The contact plate and contact sensor are used in conjunction with the IDD to apply a small preload when it places the SH holding it firmly against the target. The electronics board contains power supplies/conditioners, the dedicated CPU, different kinds of memory, firmware, and associated circuitry for instrument control and data processing. The SH of the miniaturized Mossbauer spectrometer MIMOS II has the dimensions (5 x 5.5 x 9.5) cm and weighs only ca. 400 g. Both 14.4 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously by four Si-PIN diodes. The mass of the electronics board is about 90 g [36],... 

Because of the complexity of sample preparation, backscatter measurement geometry is the choice for an in sim planetary Mossbauer instrument [327]. No sample preparation is required, because the instrument is simply presented to the sample for analysis. Both 14.41 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously. 

One of the major advantages of this design is the multimass ion detection capability, i.e., the translational energy distributions of many different masses can be detected simultaneously. In order to detect different masses simultaneously, good mass resolution is necessary. It depends on the distance between the images of adjacent masses and the image width of each mass in the mass axis. 

Fig. 3.9. Principle of a wide field FLIM system with simultaneous detection of two time gates. The fluorescence image is split into two images and one of the images is optically delayed with respect to the other. Both images are detected simultaneously with the same time-gated detector.

PET uses positron ([)1 )-emitting isotopes as the signaling unit. Positrons are antimatter and annihilate when they encounter an electron, giving rise to two photons 180° to one another. The emission of the photon pairs must be detected simultaneously to give rise to images showing the localization of the isotope (Fig. 2). 

Our project to test a Tandem accelerator for multi-beam detection was then to modify the accelerator analyzing magnet such that the various beams could be dispersed and detected simultaneously, to design an injection system to appropriately process the different isotopic beams from the ion source for injection into the accelerator, and to construct an ion-source to allow us to routinely handle small samples. Our interests at present lie in radiocarbon and radioberyllium studies, and so we have designed this system to accommodate these isotopes. 

We have recently demonstrated (Beer et al., 1995b,c) that it is possible electrochemically to detect simultaneously the presence of two different cations bound in the redox-active ferrocene bis-crown ether receptor [15] as shown in Fig. 10. 

Similar to the discovery of many other elements, cerium was detected simultaneously by several different scientists. In 1803 the Swedish chemist Jons Jakob Berzehus (1770—1848)... 

An alternative approach is to analyze the samples using procedures or instrumentation that will give the maximum amount of data for each sample. For example, recent advances in atomic spectroscopy, i.e., inductively coupled argon plasma emission spectroscopy (ICP-AES), allow 20 to 30 elements to be detected simultaneously. 

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