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Bar ripple

Bar ripples have a rectangular cross section in the y-z plane. Their longitudinal form-factor profiles are Gaussian or Lorentzian.

Constructors

BarGauss(L, W, H)
BarLorentz(L, W, H)

Parameters:

  • L, length
  • W, width
  • H, height

For a rectangular longitudinal profile, use Box.

Usage

As for any other Form factor.

Implementation

Class Bar inherits from the interface class Formfactor.

Form factor is computed as

$$ F(\mathbf{q}) = f_\parallel(q_x) f_\bot(q_y,q_z), $$

where $$ f_\bot(q_y,q_z) = WH \space \exp\Big(iq_{z}\dfrac{H}{2}\Big) \space \text{sinc}\Big(q_{y}\dfrac{W}{2}\Big) \space \text{sinc}\Big(q_{z}\dfrac{H}{2}\Big).$$

Corresponding factor $ f_\parallel(q_x) $ is chosen according to longitudinal profile.

Volume has been validated against $$V=LWH.$$

Scattering

Scattering by uncorrelated, oriented “BarLorentz” ripples for horizontal incidence. Rotation around $z$ axis:

Generated by the SAS form-factor example (particle_geometry=BarLorentz).