porod

Porod function

Parameter	Description	Units	Default value
scale	Source intensity	None	1
background	Source background	cm-1	0.001

The returned value is scaled to units of cm^-1 sr^-1, absolute scale.

This model fits the Porod function

$$I(q) = C/q^4$$

to the data directly without any need for linearisation (cf. Log I(q) vs Log q).

Here $C = 2\pi (\Delta\rho)^2 S_v$ is the scale factor where $S_v$ is the specific surface area (ie, surface area / volume) of the sample, and $\Delta\rho$ is the contrast factor.

For 2D data: The 2D scattering intensity is calculated in the same way as 1D, where the q vector is defined as

$$q = \sqrt{q_x^2+q_y^2}$$

Fig. 113 1D plot corresponding to the default parameters of the model.

Source

porod.py

References

1. G Porod. Kolloid Zeit. 124 (1951) 83
2. L A Feigin, D I Svergun, G W Taylor. Structure Analysis by Small-Angle X-ray and Neutron Scattering. Springer. (1987)

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