Neutron Scattering - JUWEL - Forschungszentrum Jülich

6 H. Frielinghaus, M.-S. Appavou
Fig. 3: Measured scattering curve of POO10-PEO10 micelles. The bright green data are measured
at a longer wavelength, and are not intended to be repeated in the lab course. Here you
can see, however, the Q −1 behavior, which clearly speaks for the cylindrical shape of the micelle
core. The dark green and blue dots are measured in the lab course. The sharp drop of the
curve at about 0.1 ˚A −1 shows the Guinier region of the cylinder cross section. This is evaluated
in further detail. Two minima and maxima follow at higher scattering vectors Q before the
incoherent background is noticeable. Black data points, shows the curve without background
(moved down to clarify the distinction).
the cylinder can be determined from scattering data, when plotting ln(Q×dΣ/dΩ) as a function
of Q 2 .
8 Evaluation of the POO10-PEO10 Scattering Curves
The entire scattering curve is first plotted in a log-log representation (Fig. 3). While in the
shown diagram, the curve is measured to even smaller Q, the larger Q values suffice for the
lab course ranging from about 0.006 up to 0.2 ˚A −1 . We see a strong drop in intensity at about
0.01 ˚A −1 . In this area the Guinier region of the cylinder cross section is found. Note that the
contrast was chosen in a way, such that only the micelle core is visible. At higher Q two minima
and maxima are found, which describe the sharp boundary of the micelle core. These two
oscillations become clearly visible when the incoherent background is subtracted. It will be sufficient
for the lab course to calculate the average of seven data points from the highest scattering
vectors and subtract it. The quality of the measurement is only visible in this representation.
The basis for our further analysis is the Guinier-plot (Fig. 4). In the Gunier-plot ln(Q×dΣ/dΩ)
is plotted against Q 2 . On the one hand, the data points show no significant slope for the smallest
Q. On the other hand the examined Q values cannot be too big, because then the Guinier