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FickDiffusionSQE

Description

This fitting function models the dynamic structure factor for a particle undergoing jump diffusion using Fick’s law for diffusion [1].

\[ \begin{align}\begin{aligned}S(Q,E) = Height \cdot \frac{1}{\pi} \frac{\Gamma}{\Gamma^2+(E-Centre)^2}\\\Gamma = DiffCoeff \cdot Q^{2}\end{aligned}\end{align} \]

where:

  • \(Height\) - Intensity scaling, a fit parameter

  • \(DiffCoeff\) - diffusion coefficient, a fit parameter

  • \(Centre\) - Centre of peak, a fit parameter

  • \(Q\) - Momentum transfer, an attribute (non-fitting)

Attributes (non-fitting parameters)

Name

Type

Default

Description

Q

WorkspaceIndex

Properties (fitting parameters)

Name

Default

Description

Height

1.0

scaling factor

Centre

0.0

Shift along the X-axis

DiffCoeff

2.3

Diffusion coefficient (10^(-5)cm^2/s)

References

Categories: FitFunctions | QuasiElastic

Source

C++ header: FickDiffusionSQE.h

C++ source: FickDiffusionSQE.cpp