Loading [MathJax]/jax/output/HTML-CSS/jax.js

InelasticDiffRotDiscreteCircle

Description

Summary

This fitting function models the inelastic part of the dynamics structure factor of a particle undergoing discrete jumps on N-sites evenly distributed in a circle. The particle can only jump to neighboring sites. This is the most common type of discrete rotational diffusion in a circle.

S(Q,E)≡=eiEt/I(Q,t)dt=1πN1l=1Al(Q,r)τ1l(τ1l)2+E2
Al(Q,r)=1NNk=1j0(2Qrsin(πkN))cos(2πlkN)
τ1l=4τ1sin2(πlN)

with h = 4.135665616 meV ps.

This function makes up the inelastic part of DiffRotDiscreteCircle.

Attributes (non-fitting parameters)

Name Type Default Description
N      
Q      
WorkspaceIndex      

N (integer, default=3) number of sites - Q (double, default=0.5) Momentum transfer - WorkspaceIndex (integer, default=0)

Properties (fitting parameters)

Name Default Description
Intensity 1.0 scaling factor [no units]
Radius 1.0 Circle radius [Angstroms]
Decay 1.0 Inverse of transition rate, in nanoseconds if energy in micro-ev, or picoseconds if energy in mili-eV
Shift 0.0 Shift in the centre of the peak

Categories: FitFunctions | QuasiElastic