Resolution background scatter

The one major difficulty with use of a flow cell is that the combination of pipe cleaner fibers and a large volume of mother liquor around the crystid greatly increases the background scatter of X-rays, particularly in the 3 A resolution region. For diffractometric data collection—and, probably, for area detector work as well—this problem is not serious, but... 

Four major computational steps are necessary to separate the individual peaks and the different profile-broadening components (i) correction and normalisation of the diffraction data, (ii) resolution of the total peak scattering from the so-called background scatter, and resolution of crystallographic, para-crystalline, and amorphous peaks from each other, (iii) correction of the resolved profiles for instrumental broadening, (iv) separation of the corrected profiles into size and distortion components. In this paper we will discuss these steps in turn, but most attention will be paid to the hitherto largely neglected step of profile resolution. 

Error Analysis. The difficulties encountered in resolving peak profiles from each other, and at the same time determining the background scatter, call to question the extent of the error involved in this type of analysis, given that the final resolution appears realistic in the light of known information about the structure of the material. The problem of error in profile resolution has been considered (14) in terms of the equatorial trace of a viscose rayon fibre specimen which is similar to Fortisan, Figure 5 ... 

It has been demonstrated, how the utilization of the concept of projections can help to analyze two-dimensional SAXS patterns with fiber symmetry quantitatively. Because the computation of long tanging integrals is involved in this method, a prerequisite for successful analysis is the careful choice of a small beam stop, a wide vacuum tube, a rather short distance between sample and detector and a fast and linear detector. By doing so one can hope to register both all the reflections and also the important background scattering with required accuraQ and spatial resolution. 

---