Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
Chem Commun (Camb). 2012 May 25;48(42):5103-5. doi: 10.1039/c2cc30609c. Epub 2012 Apr 20.
Structural patterns that have the same spatial periodicity but a phase offset give rise to peaks and anti-peaks (negative-going peaks) at the same q value in the SAXS structure function S(q). As an example, in ionic liquids we often find charge alternation, and at the distance where one finds a density enhancement of charges of the same type one also finds a depletion of charges of opposite sign. Another such situation arises with polar-apolar densities. At distances where there is enhancement of same-type (polar-polar or apolar-apolar) densities there is also a depletion of opposite-type (polar-apolar) density. This gives rise to prepeaks and what we call same spatial periodicity anti-prepeaks.
具有相同空间周期性但存在相位偏移的结构模式会在 SAXS 结构函数 S(q) 中在相同 q 值处产生峰和反峰（负峰）。例如，在离子液体中，我们经常发现电荷交替，在发现同种电荷密度增强的距离处，也会发现相反电荷密度的耗尽。另一种情况出现在极性-非极性密度中。在同种类型（极性-极性或非极性-非极性）密度增强的距离处，也会出现相反类型（极性-非极性）密度的耗尽。这会导致前峰和我们所说的相同空间周期性反前峰。
