AKIMA INTERPOLATION - A TOOL USED IN DIRECT SLIT-LENGTH DESMEARING PROCEDURES OF NON-FREQUENCY-LIMITED X-RAY-SCATTERING CURVES

X-ray small- and medium-angle scattering of partially ordered or semic rystalline materials is composed of background scattering from the for m scattering of the components and from the amorphous phase and of pea ks from the scattering of the crystallites. By the slit geometry of X- ray diffractometers constructed for registration of small- and medium- angle X-ray scattering, the diffuse scattering and the peaks are disto rted and the peak positions and half-widths are changed. A program mod ule based on the Akima interpolation [Akima (1970). J. Assoc. Comput. Mach. 17, 589-602] is proposed for calculation of the first derivative of the complete smeared scattering curve, which is then explicitly us ed in direct collimation-correction procedures. The desmearing of scat tering curves from semicrystalline starch samples proves the convenien ce of the method for low-noise conditions and exhibits a significant g ain of measuring time in comparison with data of comparable accuracy b ut measured with Soller-slit collimation systems or desmeared with dir ect methods using frequency filtering.