Effective measurement slit

The factor A2 describes the influence of the profile of the analysis line and the influence of the effective measurement slit. In the case of photoelectric measurements the latter is the exit slit width of the spectrometer. This contribution is only... 

The factor A2 describes the influences of the profile of the analysis line and the effective measurement slit. For photoelectric measurements, the latter is the exit slit width. r, of the spectrometer. This contribution is relevant only when sjs ff < 2, which is practically the case only for photographic measurements where the line profile is scanned with a very narrow densitometer slit. For photoelectric measurements, A2=sjscff 1, as the exit slit width must be larger than the effective line width because of the thermal and mechanical stability of the system. The detection limit is a relevant figure of merit for an analytical method (Section 21.3.1). It can be written for AES ... 

The ratio 0/0 is thus a measure of the enhancement of the energy of adsorption in a micropore as compared with that on an open surface. In curve (i) of Fig. 4.9 this ratio is plotted as a function of d/r and, as is seen, the enhancement is still appreciable when d = l-Sr, but has almost disappeared when d = 2r , i.e. when the slit is only two molecular diameters wide. Even when d/r = 1, which corresponds to a single molecule tightly packed into the width of the slit, the enhancement is only 1-6-fold. The effect... 

Usually, particle size has relatively little effect on Raman line shapes unless the particles are extremely small, less than 100 nm. For this reason, high-quality Raman spectra can be obtained from powders and from polycrystalline bulk specimens like ceramics and rocks by simply reflecting the laser beam from the specimen surface. Solid samples can be measured in the 90° scattering geometry by mounting a slab of the solid sample, or a pressed pellet of a powder sample so that the beam reflects from the surface but not into the entrance slit (Figure 3). 

The answer is a. (Hardman, pp 885-8870 Lovastatin should not be used in patients with severe liver disease. With routine use of lovastatin, serum transaminase values may rise, and in such patients the drug may be continued only with great caution. Lovastatin has also been associated with lenticular opacities, and slit-lamp studies should be done before and one year after the start of therapy There is no effect on the otic nerve. The drug is not toxic to the renal system, and reports of bone marrow depression are very rare There is a small incidence of myopathy, and levels of creatinine kinase should be measured when unexplained muscle pain occurs. Combination with cyclosporine or clofibrate has led to myopathy There is no danger in use with bile acid sequestrants. 

Experimentally, several precautions must be taken if reliable Raman data are to be obtained from solution studies. Firstly, the instrumental slit-width should be appreciably smaller than the half-width of the band to be studied. This means that slits wider than 2 cm-1 are to be avoided. Secondly, photolytic decomposition of the sample and local boiling of the solvent have also to be avoided. Careful choice of laser frequencies, use of a low incident power and, if necessary, sample spinning are indicated. The need for a relatively high solute concentration usually means that there is little choice of solvent. Particularly for coloured samples the presence of a vestigal resonance Raman effect must be tested by measurements with a variety of... 

The dispersive (+ n, - m ) mode has already been seen clearly with the duMond diagrams, Figure 2.10. Here, the curves are no longer identical and the crystals must be displaced from the parallel position in order to get simultaneous diffraction. As the crystals are displaced, so the band of intersection moves up and down the curve. When the curves become very different, the K 1 and K 2 intensities are traced out separately. Then the peaks are resolved in the rocking curve, and if no better beam conditioner is available it is important in such cases to remove the K 2 component with a slit placed after the beam conditioner. A slit placed in front of the detector, with the detector driven at twice the angular speed of the specimen, also works very well. This is in effect a low resolution triple-axis measurement. 

To effect this measurement the slit bandwidth of the atomic absorption apparatus is 1 nm. What does this parameter represent ... 

Equation 18-14 says that, at low concentration, emission intensity is proportional to analyte concentration. Data for anthracene in Figure 18-22 are linear below 10 6 M. Blank samples invariably scatter light and must be run in every analysis. Equation 18-14 tells us that doubling the incident irradiance (P0) will double the emission intensity (up to a point). In contrast, doubling P0 has no effect on absorbance, which is a ratio of two intensities. The sensitivity of a luminescence measurement can be increased by more than a factor of 3 by the simple expedient of using a mirror coating on the two walls of the sample cell opposite the slits in Figure 18-20.15... 

Spectra were run on a Perkin-Elmer model 125 grating spectrophotometer at room temperature, ignoring the heating effect of the IR beam. Reference beam attenuation was used. The spectral slit width was less than 3 cm-1 in the region 1600-1400 cm-1. Optical density measurements were carried out as previously described (19). 

---