# linear_pearls

Linear pearls model of scattering from spherical pearls.

Parameter | Description | Units | Default value |
---|---|---|---|

scale | Source intensity | None | 1 |

background | Source background | cm^{-1} |
0.001 |

radius | Radius of the pearls | Å | 80 |

edge_sep | Length of the string segment - surface to surface | Å | 350 |

num_pearls | Number of the pearls | None | 3 |

sld | SLD of the pearl spheres | 10^{-6}Å^{-2} |
1 |

sld_solvent | SLD of the solvent | 10^{-6}Å^{-2} |
6.3 |

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

This model provides the form factor for \(N\) spherical pearls of radius \(R\) linearly joined by short strings (or segment length or edge separation) \(l\) \((= A - 2R)\). \(A\) is the center-to-center pearl separation distance. The thickness of each string is assumed to be negligible.

**Definition**

The output of the scattering intensity function for the linear_pearls model is given by (Dobrynin, 1996)

where the mass \(m_p\) is \((SLD_{pearl}-SLD_{solvent})*(volume\ of\ N\ pearls)\). V is the total volume.

The 2D scattering intensity is the same as P(q) above, regardless of the orientation of the q vector.

**References**

A V Dobrynin, M Rubinstein and S P Obukhov, *Macromol.*,
29 (1996) 2974-2979