SMALL ANGLE X-RAY AND NEUTRON SCATTERING

Miloš Steinhart¹ & Josef Pleštil

Institute of Macromolecular Chemistry, Prague, Czech Republic

¹Permanent address: University of Pardubice, Studentská 84, Czech Republic

In early thirties of the twentieth century it was realized that diffuse scattering in the neighbourhood of the primary beam carries important structural information. In forties a great development started to employ this effect and provide the science with a well established technique, as we know today. Methods of small angle scattering (SAS) are suitable for the investigation of the structures (not necessarily periodic) with, so called, colloidal dimensions, i.e., from one up to several hundreds of nm.

At present, the SAS methods are divided into several groups, each using mainly some special and dedicated techniques, for instance, surface scattering. However, the main aspect of division is the type of radiation used. So there are SAXS and SANS techniques, using X-rays and neutrons, respectively. In spite of the totally different nature of interaction of electromagnetic waves and neutrons with matter, the basic theory of scattering in the small angle region is the same. It should also be stressed that although the interpretation of SAS data can provide a couple of very general structural model independent parameters, the information hidden in the measurements is used the more effectively, the more independent knowledge about the studied system is available in advance. It is not surprising that many important results have been obtained combining SAS with other methods. Thanks to different contrast, even a combination of the closely related SAXS and SANS techniques is often very fruitful.

This contribution is meant to give an insight into the basic theory and to present examples of the recent SAS studies, thus illustrating the extent of applications of this method. The main objective is to provide experts from another fields with an idea, what kinds of problems can be studied and what information can be expected.

In the first part, the basic principles of scattering starting from one atom to bigger entities are given. Then the types of structural characteristics, to which SAS methods are sensitive, are shown. Next the main techniques of data interpretation are outlined. In last part, the use of SAS methods in various fields and their main achievements are illustrated. We shall concentrate on SAXS, both on conventional and synchrotron radiation sources, but some examples of SANS results will also be shown.

Some useful texts we can recommend are:

[1] A. Guinier, G. Fournet: Small-Angle Scattering of X-Rays, J. Willey, NY 1955

[2] O. Kratky: SAXS, Progr. in Biophys. 13, 105, 1963

[3] Small-Angle X-Ray Scattering, O. Glatter & O. Kratky, Eds., Academic Press, London 1982,

[4] Neutron, X-Ray and Light Scattering: Introduction to an Investigative Tool for Colloidal and Polymeric Systems, P. Lindner & T. Zemb, Eds. N. Holland, Delta 1991

[5] http://scattering.tripod.com/#SAXS

The research was supported by the Grant Agency of the Czech Republic (Project No.: 203/00/13170) and the Academy of Sciences of the Czech Republic (Project No.: AVOZ 4050913)