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=1πl=1N1Al(Q,r)τl1(τl1)2+E2
Al(Q,r)=1Nk=1Nj0(2Qrsin(πkN))cos(2πlkN)
τl1=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

Source

C++ header: InelasticDiffRotDiscreteCircle.h

C++ source: InelasticDiffRotDiscreteCircle.cpp