Sequential scanning

Common to all narrow-bandwidth excitation schemes is sequential scanning of an experimental parameter in order to adjust the Raman shift in CRS detection. In order to obtain an entire CRS spectrum, this is not only time consuming but also prone to sources of noise induced by fluctuations in laser pulse parameters. As a consequence, dynamical changes in a CRS spectrum are difficult to follow. This problem can be circumvented by use of multiplex CRS spectroscopies [48, 49], which will be discussed in combination with CARS and SRS microscopy in Sects. 6.3 and 6.4, respectively. 

Kimberly MM, Paschal DC. 1985. Screening for selected toxic elements in urine by sequential-scanning inductively-coupled plasma atomic emission spectrometry. Anal Chim Acta 174 203-210. 

The application of multichannel light detection devices to the measurement of CD will significantly improve the technique and allow extension into areas not presently accessible by conventional, sequentially scanned CD. For example, multichannel devices will enable SNR improvements via spectral averaging. Alternately, a complete CD spectrum can be obtained on a transient species in the time domain required for a single wavelength... 

Isotope Ratios and Internal Standardization The ability to extract all ions from an incoming ion beam simultaneously allows the TOF-MS to provide better precision than sequentially scanned ICP-MS instruments. Provided that the dominant source of noise is multiplicative in nature, all elements and isotopes should experience the same perturbations. Therefore, ratioing techniques such as isotopic dilution should allow compensation for drift and source noise, and isotope-ratio measurements should improve in precision. 

The main disadvantage of such a series of sequential scans is the large number of experiments required to establish the area of optimum capacity factors (see for example refs. [520] and [521]). 

SCAN Performs a uniform sequential scan of conformational... 

Automatic searches of conformational hyperspace may be requested using the multi-level bond rotation algorithm described above. A selection is made for a uniform sequential scan, a random scan, or a multi-dimensional minimization search of the conformational energy surface. (As indicated above, prototype versions of CAMSEQ/M provide only the sequential scan mode.)... 

When a triple labelling is used, the use of sequential scanning is preferred. In the normal modus, all the signal are simultaneously acquired in different channels, which in the case of multiple labelling can result in crosstalk, which can ultimately lead to misleading co-localization results. 

In the precursor ion scan, the first mass analyzer (Qj) sequentially scans all precursor ions into the collision cell (Figure 7(c)) for fragmentation. The second analyzer (Qj) is then set to transmit a single specified ion product. The resulting mass spectrum is then a record of all the precursor ions that give rise to the specified common product ion, such as, for example, the metabolites of a particular drug, or class of compounds, which can be fragmented to a common structural moiety. The precursor ion scan can be carried out only with tandem-in-space instruments. 

Multichannel spectrometers may contain, in addition to the fixed channels, a scanning channel in which a moving crystal and counter can sequentially scan the entire spectrum, just as in a single-channel instrument. This feature is useful for qualitative analysis or for quantitative determination of an element for which a fixed channel has not been preset. 

SPD. The diodes in an SPD must be sequentially scanned by the shift registers and therefore a real random access cannot be accomplished. However, a pseudo-random access (fast access) readout mode is possible. In this mode, diodes that contain no relevant spectral information are skipped (not read) at a high scan rate, e.g., 2 MHz, whereas those containing desired... 

CID devices such as the General Electric RA-128 can also be fabricated to provide random addressing of the array. With this capability only the desired pixels need be interrogated instead of sequentially scanning through the whole array as is required in most other solid-state devices. Therefore, faster readout speeds are possible for rapid analysis. 

ICP-MS elevated cost (although less than most molecular MS instrumentation), possibly troublesome polyatomic interferences, low ionization efficiency for biologically important elements (Se, S, P, halogens), and, in most commercially available instruments, sequentially scanning nature of mass analyzer and detection system. 

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