Spectral sensitivity

As in chemical sensitization, spectral sensitization is usually done after precipitation but before coating, and usually is achieved by adsorbing certain organic dyes to the silver haUde surfaces (47,48,212—229). Once the dye molecule is adsorbed to the crystal surface, the effects of electromagnetic radiation absorbed by the dye can be transferred to the crystal. As a result of this transfer, mobile electrons are produced in the conduction band of the silver haUde grain. Once in the conduction band, the electrons are available to initiate latent-image formation. 

Photography, Silver Halide, Chemical Sensitization, Spectral Sensitization, Latent Image Formation (James). 

The major characteristics of the photomultiplier with which the user is generally most concerned include (1) sensitivity, spectral response, and thermal emission of photocathodes (2) amplification factor and (3) noise characteristics and the signal-to-noise ratio. 

Chemical Sensitization, Spectral Sensitization, and Latent Image Formation in Silver Halide Photography By T. H. James, 1600 Ala Moana Boulevard,... 

Three advantages of IR microscopic imaging for the studies of permeation into skin are clear from the above data. First, the location of exogenous material is directly monitored. Second, conformation-sensitive spectral features provide useful indicators of changes in molecular structure. Third, if the exogenous material perturbs the molecular structure of the native skin components, the nature and locahon of the disruption can be imaged directly from the spectra of the endogenous material. 

The recent availability of tunable dye lasers has markedly enhanced our ability to inquire into the chemistry and physics of combustion systems. The high sensitivity, spectral and spatial resolution, and non-perturbing nature of laser induced fluorescence makes this technique well suited to the study of trace chemistry in complex combustion media. A barrier to the quantitative application of fluorescence to species analysis in flames has been the need to take into account or bypass the effects of quenching. The use of saturated fluorescence eliminates quenching as a problem and has the further advantage that fluorescence intensity is insensitive to variations in laser power (1, 2 ). However, the generation of high concentrations of excited states under saturated excitation in an active flame environment opens up the possibilities for laser induced chemistry effects that also must be taken into account or avoided (3,4,5). 

If sensitivity, spectral resolution, and minimal photobleaching are primary concerns, single narrow band filters sets with black and white CCD camera detection is the best option. Image registration shifts are minimized in today s filters by the use of polished substrates and virtually eliminated by using filter sets made to zero shift specifications. 

The problem is to prepare solutions suitable for the desired analytical results. Once a homogeneous analytical solution is available, the differences between the techniques used with dissolved metals are no longer great since the same nebuliser systems can be employed. For the determination of major components it is preferable to use less sensitive spectral lines of the same elements rather than use greater dilutions. 

Keywords Magic-Angle Spinning NMR Sample rotation Rotor size Selectivity Sensitivity Spectral resolution... 

Manganese measurements were performed on diluted sediment because the Mn concentration had to be determined on the poorly sensitive spectral line at... 

IR spectra were recorded with a Perkin Elmer 1500 Fourier Transform IR spectrophotometer with a TGS detector. Typically 200 scans were averaged for each sample to improve the signal-to-noise ratio and allow spectral subtraction at high sensitivities. Spectral subtraction was performed using the 973 cm-1 PP band (which is largely insensitive to variations in helical content) as the reference band to be suppressed to zero. Iodometric analysis of oxidized films were performed as described previously (8). Stress-strain measurements were performed on 4 mm film strips on an Instron Model 1123 at 500 % min-1. 

Fourier transform IR (FTIR) spectroscopy (54), which offers major benefits over conventional IR spectroscopy from greater sensitivity, spectral resolution, and substantially better signal-to-noise ratios, seems capable of furnishing equally good estimates of C /C and H /H (55). In this case, one measures Hal, derives from the stoichiometric relationship H /C = 1.8, and calculates Car by difference. However, applied to coal (as distinct from certain coal derivatives), FTIR spectroscopy has been mainly used to obtain better data for substituent functions (56, 57) and what are currently deemed to be the most authoritative data on coal aromaticity have all been recorded by 13C NMR spectroscopy. 

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