This fitting function models 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.
Markov model for jumps between neighboring sites:
The Decay fitting parameter is the inverse of the transition rate. This, along with the circle radius , conform the two fundamental fitting parameters of the structure factor :
The transition rate, expressed in units of energy is , with h = 4.135665616 meV THz.
When using InelasticDiffRotDiscreteCircle, he value of Q can be obained either though the Q attribute or can be calucated from the input workspace using the WorkspaceIndex property. The value calculated using the workspace is used whenever the Q attibute is empty.
Methyl Rotations can be modelled setting N=3. In this case, the inelastic part reduces to a single Lorentzian:
If, alternatively, one models these dynamics using the Lorentzian function provided in Mantid:
Then:
Name | Type | Default | Description |
---|---|---|---|
N | |||
NumDeriv | |||
Q |
Name | Default | Description |
---|---|---|
f0.Height | 1.0 | Scaling factor to be applied to the resolution. |
f0.Centre | 0.0 | Shift along the x-axis to be applied to the resolution. |
f0.Radius | 1.0 | Circle radius [Angstroms] |
Intensity | 1.0 | scaling factor [arbitrary 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 domain |
Categories: FitFunctions | QuasiElastic