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J. Innerlohinger, M. Villa, M. Baron, O. Glatter:
"Ultra-small-angle neutron scattering from dense micrometre-sized colloidal systems: data evaluation and comparison with static light scattering";
Journal of Applied Crystallography, 39 (2006), 202 - 208.

Ultra-small-angle neutron scattering (USANS) probes the same q regime as
static light scattering (LS), making USANS an additional tool for the study of
structures between 100 nm and 10 mm. Dense oil-in-water emulsions, which have
already been characterized intensively by light scattering, are investigated in this
study as a model system using USANS. The two basic problems of such
scattering studies are the following: on the one hand, one has to use different
scattering theories for USANS and LS, and on the other hand, in both cases one
has to deal not only with particle interactions but also with multiple-scattering
effects. For neutron scattering it is always possible to use the simpler Rayleigh-
Debye-Gans (RDG) theory instead of the Lorenz-Mie theory, which generally
describes light scattering from micrometre-sized globular objects. The samples
have different contrasts in neutron and light scattering, such that only lowcontrast
(close to index match) LS data can be interpreted by the RDG theory.
The data evaluation is performed by means of the generalized indirect Fourier
transformation (GIFT) method, which enables the simultaneous calculation of
the form and structure factors. The results are discussed and compared with
those from light scattering experiments, taking into account the advantages of
both methods. The effect of multiple scattering and its influence on data
evaluation is also examined. Data evaluation by applying the GIFT method
works well for both neutron and light scattering data, with results of comparable
quality. The advantages of light scattering are the fast data acquisition and the
large number of data points. USANS, on the other hand, covers a wider q range
and the problem of multiple scattering is not as severe as for light scattering, but
still must not be neglected.
1. Introduction
Scattering methods are a commonly used tool in the study of
colloidal systems and complex fluids (Lindner & Zemb, 2002).
Neutron (and X-ray) scattering approximately covers a size
regime from below 1 nm up to 100 nm (q range ´ 0.1-
10 nm 1), whereas static light scattering can be used to
investigate particles from 100 nm to 10 mm or more (q range ´ 1 10 4-1 10 2 nm 1). These sizes of course depend on the
setup of the instrument and the wavelength used. Thus
neutron and light scattering complement each other in the
covered size regime, and it is possible to obtain a scattering
curve over a wide q range by combining data from neutron
(high q) and light scattering (low q). Therefore, neutron and
light scattering can be used to investigate different size
domains of a sample. As the techniques do not cover the same
q range, a direct comparison of the scattering curves is
normally impossible.
Ultra-small-angle neutron scattering (USANS) now
provides access to the same q range (and size regime) as static
light scattering (LS), thus making a direct comparison of the
results possible. In this study, we compare USANS data with
LS data using different types of dense oil-in-water emulsions
as model systems. Such emulsions have already been intensively
studied by LS (Lindner et al., 2001). To suppress
multiple scattering, we use a special sample cell with an
adjustable, very small sample thickness. This sample cell is
used for the LS and USANS experiments.
The data evaluation is performed by the generalized
indirect Fourier transformation (GIFT) technique. This
method can simultaneously calculate the form and structure
factors from the scattering curves with minimum a priori
information needed. As the GIFT method is based on the
Rayleigh-Debye-Gans (RDG) theory, neutron data have the
advantage that they can always be evaluated using this
method. Light scattering is usually described by the Lorenz-

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