Neutron Scattering

scattering to spin-flip scattering for a coherent scatterer is rather high, up to 1 -I-II+
0 .98, while on average the performance is about 0 .95 °70 .
The following example is related to studies of structural properties of polymer glassec,
in which polarization analysis can be quite useful . Besides separating the coherent structure
factor, separated incoherent scattering intensities can be used for an intrinsic absolute
calibration . An example is shown in Fig . 4-17 . In this experiment[17] one bas also used
partial isotopic substitution of H by D to mark and to contrast the side-chains and the
backbone of different polymers (polyalcylmethacrylates) .
2
0
2
'H,
(Ï'-'CI-CD, CD--CD -CD . CD,-CD,
0
Figure 4 .17 : Coherent structure factor of a partially deuterated polymer . Note that
by separatinn of the coherent and incoherent scattering one obtains a precise absolute
intrinsic calibration . Two measurements are displayed in the figure (bottom right) [with
.\ = 3 .3 Â (diamonds) and A = 5 .3 Â (circles)] demonstrating the excellent reproducibility
of the data. The peak at lower _C is due to inter-chain correlations between different
polymer "backbones" and the peak around Q 1 .4Â -1 can be related to intea-chain
correlations along the polymer, the ones between the side-chains of a polymer .
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