Small angle neutron scattering contrast factors

Small angle neutron scattering measurements were carried out with the PACE diffractometer at the Laboratoire Leon Brillouin, (CE Saclay, France). The q range observed was 3.4 lO" to 0.2 A l. Samples were prepared in deuterated instead of ordinary water to achieve a suitable value for the neutron contrast factor. 

Figure 3 shows the small-angle neutron scattering (obtained at Ris0 National Laboratory, Denmark) from a dilute sample of cj) = 0.02 where the oil and water has been contrast matched resulting in coherent scattering from the surfactant film alone [5]. A fit to the data, shown as a solid line, corresponds to the form factor of a spherical shell of radius fhc = 75 A and a relative polydispersity c/rhc = 0.16. This polydispersity contains contributions from both size (volume) and shape polydispersity [5]. Their relative contributions are not accurately known, however, contrast match experiments indicate that it is the shape polydispersity which dominates. 

S A N S can be employed to study both homogeneous as well as heterogenous blends and various information can be derived by analysis of the differential scattering cross-section, d2(Q)/dQ (cm ), where d2(Q) (neutron s ) is the number of neutrons scattered per second into a small solid angle, dQ. The measured intensity, I Q), is related to d 2(Q)/d Q and depends on various parameters such as the incident flux, resolution of the detector, detector efficiency, and so on. It is also a function of the contrast factor (Ag), which is defined as the square of the difference of the scattering length density of the scattering centers, for example, the particle and the matrix. This quantity is calculated from ... 

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