Sample transparency

Instrumental and sample parameters error in the wavelength, sample transparency, etc. 

Determination of Sn by wave-length dispersive XRF requires special corrections for sample transparency and background LOD 3.5-4 ppm34. 

Thus, varying the frequency of an applied electric field at a given temperature, one may pass over from homeotropic orientation of the sample (transparent film) to the mode of EHD instability and reverse. This reveals interesting perspectives for controlling the optical properties of polymeric films. 

Refractive index grating and heterodyne detection For a sample transparent at the readout wavelength, a pure refractive index or phase grating builds up, with contributions from both the temperature and the concentration gratings. In analogy to Eqs. (15) and (19), it is expressed as... 

Sample Transparent, bubble and particulate-free liquids Powder samples require diffuse reflectance probe Transparent liquid, thin solid pellets and ideal for gases Special ATR probes needed Same probe is used for all samples liquids, slurries, emulsions, powders, solids, samples with particulates, and bubbles... 

Direct measurement of MIPs (Sections 20.2.5.4., 20.2.5.5. and 20.2.5.9.) should also yield new opportunities. One envisages soaking a polymer film in a sample solution (or, as in Section 20.2.3., exposing the film to a gaseous analyte) then inserting the film into the appropriate device and, from the observed change in optical properties, calculating the concentration of analyte in the sample. Transparent MIPs such as those developed by Steinke et al. (Section 20.2.2.) should prove extremely useful in such techniques. 

Using all Bragg peaks which have been indexed and the associated observed Bragg angles, more accurate unit cell dimensions and, if applicable, systematic experimental errors, e.g. sample displacement, sample transparency, or zero shift, which are described in section 2.8.2, Chapter 2, should be refined by means of a least squares technique (see section 5.13, below). 

The specimen displacement parameter usually varies from sample to sample and it usually takes up some of the effects of sample transparency. For a properly aligned goniometer, the zero shift error should be negligible. Even if the goniometer is misaligned, the zero shift correction should remain sample independent. 

There are two different approaches for calculation of the instrumental function. The first is the convolution approach. Proposed more than 50 years ago, initially to describe the observed profile as a convolution of the instrumental and physical profiles, it was extended for the description of the instrumental profile by itself According to this approach the total instrumental profile is assumed to be the convolution of the specific instrumental functions. Representation of the total instrumental function as a convolution is based on the supposition that specific instrumental functions are completely independent. The specific instrumental functions for equatorial aberrations (caused by finite width of the source, sample, deviation of the sample surface from the focusing circle, deviation of the sample surface from its ideal position), axial aberration (finite length of the source, sample, receiving slit, and restriction on the axial divergence due to the Soller slits), and absorption were introduced. For the main contributors to the asymmetry - axial aberration and effect of the sample transparency - the derived (half)-analytical functions for corresponding specific functions are based on approximations. These aberrations are being studied intensively (see reviews refs. 46 and 47). 

Ellipsometry — Film thickness — Polarized light Sample transparent 88, 91... 

Figure 10. Phase diagram of PS-1.2SK / PMMA-6.3SK. (x) - cloud samples, (°) transparent samples,...

Despite numerous studies, the observation of LAM in other polymers proved elusive for quite some time (105,106). For isotactic polypropylene, LAM was not obtained imtil 25 years after the initial observation. The first LAM observation was for an isotactic polypropylene prepared under special conditions of extrusion and orientation (107). Both sample transparency and the preferential reduction in Rayleigh scattering made the observation possible (Fig. 10). LAM has now been observed in a number of polymer systems such as PTFE, polyoxy methylene, PEO,... 

Before data are collected, it should be ascertained that the diffractometer system is well aligned and that a suitable measurement configuration is chosen. In case of a flat-plate reflection geometry, a correct combination of optic elements (slits and monochromator system) and sample size should ensure that neither sample transparency nor beam overflow at low angles... 

---